Question 1

Vitamin B12 (cobalamin) fermentation: which of the following microorganisms have been used as production strains for vitamin B12?

Accepted Answer

Introduction / Context: Vitamin B12 (cobalamin) is an industrially important cofactor used in food fortification and pharmaceuticals. Multiple microbial genera are known to synthesize corrinoids, and a range of organisms have been tested or deployed as production strains depending on yield, downstream processing, and regulatory acceptance. Given Data / Assumptions: Historically and experimentally, several bacteria and actinomycetes have produced cobalamins or closely related corrinoids. Modern large-scale processes often use Propionibacterium species or Pseudomonas denitrificans, but other organisms remain documented producers in the literature. The question asks which listed organisms have been used—not which is the single best modern industrial choice. Concept / Approach: Evaluate each candidate for reported B12 or corrinoid production capability. Bacillus megaterium and several Streptomyces species have been studied for cobalamin biosynthesis, even if not today’s dominant commercial strains. Therefore, when the scope includes organisms that “have been used” in research or pilot production, “All of these” is justified. Step-by-Step Solution: List organisms widely cited for cobalamin production (Propionibacterium, Pseudomonas, certain Bacillus and Streptomyces).Check each option against literature reports for corrinoid production.Confirm that all listed organisms have documented use or potential in B12 fermentation.Select “All of these.” Verification / Alternative check: Fermentation reviews discuss diverse producers; while modern processes prefer specific strains for yield and safety, multiple genera have been explored historically. Why Other Options Are Wrong: Individual organisms (a–c): Each alone is incomplete relative to the question’s inclusive scope. None of these: Contradicted by known literature on microbial corrinoid production. Common Pitfalls: Confusing “current commercial standard” with “organisms ever used”; overlooking that research and early industrial practices included many species before process optimization converged on a few. Final Answer: All of these

Question 2

Carbon source for glutamic acid fermentation: which substrate most commonly constitutes the main carbon feed in media for industrial glutamate (glutamic acid) production?

Accepted Answer

Introduction / Context: The cost and composition of the carbon source strongly influence economics and yields in amino acid fermentations such as glutamate production with Corynebacterium glutamicum. Industrial media frequently rely on inexpensive, readily available feedstocks rather than pure sugars, provided process impurities are manageable. Given Data / Assumptions: Industrial practice often substitutes pure glucose with agricultural by-products. Molasses (cane or beet) offers a cost-effective mixture of sugars and micronutrients after appropriate pretreatment. Process control (for example, biotin limitation, aeration) drives glutamate secretion independent of whether the carbon is supplied as pure glucose or molasses. Concept / Approach: Among the options, molasses is the classic “main” carbon feed in many large-scale glutamate processes due to price, availability, and acceptable performance after conditioning. While glucose and sucrose can also be used effectively, molasses remains the textbook industrial answer to “what the medium mainly consists of” in commercial practice. Step-by-Step Solution: Consider cost and supply consistency of candidate carbon sources.Recall common amino-acid fermentation feeds used historically and currently.Recognize that molasses is frequently cited as the principal carbon source.Select molasses accordingly. Verification / Alternative check: Industrial microbiology references for amino acid fermentations list molasses as a typical primary carbon source, with pretreatments to minimize inhibitors. Why Other Options Are Wrong: Glucose/Sucrose: Effective but often costlier as primary industrial feeds. Lactose: Less common for glutamate; more associated with whey valorization. Starch hydrolysate: Possible, but molasses is the more classic, widely cited “main” component. Common Pitfalls: Equating laboratory media (pure glucose) with commercial media choices; ignoring pretreatment needs for molasses to mitigate trace metal inhibition. Final Answer: molasses

Question 3

Industrial alcohol substrates: which of the following is NOT a principal feedstock used for large-scale ethanol production by fermentation?

Accepted Answer

Introduction / Context: Traditional fermentation industries produce ethanol using carbohydrate-rich, low-cost feedstocks available at scale. Recognizing principal substrates versus marginal or emerging alternatives helps clarify classic process design and historical practice versus modern pilot projects. Given Data / Assumptions: Classic substrates include molasses (cane/beet), starch mashes (from grains), and sulphite waste liquor from pulp mills. “Principal” denotes historically dominant, widely deployed feedstocks. Wood waste contains lignocellulose and typically requires extensive pretreatment and hydrolysis; it is not a classic principal feedstock in conventional plants. Concept / Approach: Evaluate each option’s historical and industrial prevalence. Black strap molasses and sulphite waste liquor are textbook principal feeds. Starch mashes converted to fermentable sugars via amylolytic enzymes are also principal. While glucose is fermentable, purchasing refined glucose as the main feed is rarely economical compared with the above bulk sources. Wood waste, although a focus in modern cellulosic ethanol R&D, was not a principal feedstock for traditional fermentation plants. Step-by-Step Solution: List historically dominant ethanol feedstocks.Contrast with lignocellulosic materials that require advanced pretreatment.Identify the non-principal feed among options.Select wood waste as the outlier. Verification / Alternative check: Surveying industrial references shows molasses, starch hydrolysates, and sulphite waste liquor as core feedstocks; cellulosic routes from wood waste remain specialized or developmental. Why Other Options Are Wrong: Black strap molasses: Classic principal feedstock. Sulphite waste liquor: Historically important in regions with pulp industry. Glucose: While not cost-optimal, it is a direct, fermentable sugar—more principal than wood waste in legacy plants. Starch mash: A principal route after liquefaction and saccharification. Common Pitfalls: Confusing modern cellulosic ethanol research prominence with historical industrial prevalence; assuming any fermentable carbohydrate is economical at scale. Final Answer: Wood waste

Question 4

Non-ionic surfactants in β-carotene fermentation: which statement best describes the role of certain non-ionic detergents (for example, Tween-80) added to the β-carotene production medium?

Accepted Answer

Introduction / Context: In microbial β-carotene production (for example, using Blakeslea trispora or engineered yeasts), medium supplements can markedly influence flux through the carotenoid pathway. Non-ionic surfactants such as Tween-80 are sometimes added to modify membrane permeability, oxygen transfer, and nutrient availability, thereby affecting enzyme expression and activity. Given Data / Assumptions: The question concerns the functional role of a non-ionic detergent added to the fermentation medium. Desirable effects include enhanced mass transfer and modulation of membrane properties that can “steer” metabolism toward carotenoid accumulation. The supplement is not itself the carotenoid precursor molecule (such as isoprenoid intermediates). Concept / Approach: Surfactants can act as “steering” factors by altering the cellular environment—improving oxygen uptake in filamentous cultures, changing membrane fluidity, and facilitating secretion/uptake dynamics. These changes often correlate with upregulated or more effective activity of key enzymes in the mevalonate/terpenoid pathway, indirectly boosting β-carotene formation. Thus the most accurate statement is that such detergents act as steering factors influencing enzyme presence and activity rather than serving as direct precursors or classic chemical inducers. Step-by-Step Solution: Identify the additive: non-ionic surfactant (e.g., Tween-80), not a terpene or apocarotenoid.Recall physiological effects: membrane and mass-transfer modulation.Link effects to pathway: improved conditions can enhance carotenoid pathway enzyme activity.Select the description that captures this steering influence. Verification / Alternative check: Fermentation studies often report higher carotenoid titers with surfactant addition attributed to better oxygen transfer and altered cell physiology consistent with a steering effect. Why Other Options Are Wrong: Precursor: Non-ionic detergents are not biochemical precursors of carotenoids. Inducer: While titers rise, the effect is not a specific inducer–repressor mechanism; it is primarily physiological/physical. None of the above: Incorrect because a correct statement is provided. Inhibitor: Opposite of the intended effect; surfactants are used to improve, not suppress, carotenoid production. Common Pitfalls: Confusing β-ionone (an apocarotenoid fragrance molecule) with non-ionic surfactants; assuming any titer increase implies a classical genetic induction mechanism. Final Answer: It is regarded as a “steering” factor associated with bringing about the presence and activity of enzymes responsible for β-carotene formation

Question 5

Industrial microbiology: At commercial scale, how are amino acids typically overproduced and efficiently released from cells?

Accepted Answer

Introduction / Context: Amino acids such as lysine, glutamate, and threonine are manufactured at large scale by microbial fermentation. Two classic strategies are used together: push the metabolic pathway to overproduce the desired product and pull the product out of the cell efficiently to avoid feedback inhibition and product toxicity. Given Data / Assumptions: Objective: maximize amino acid titer, rate, and yield. Microbial hosts (e.g., Corynebacterium, E. coli) are engineered for flux toward target amino acids. Export or release mechanisms reduce intracellular accumulation. Concept / Approach: Regulatory mutants remove or blunt natural controls that limit pathway flux. Examples include feedback-resistant aspartate kinase for lysine/threonine and relief of repression systems. Separately, altering membrane transport or permeability, or introducing exporters, improves secretion. Combining these increases net productivity by improving both synthesis and mass transfer. Step-by-Step Solution: Identify production bottlenecks: pathway regulation and product export.Use regulatory mutations to increase flux toward the amino acid (e.g., feedback-resistant enzymes).Engineer membranes/transporters to enhance secretion or controlled leakage to reduce intracellular feedback.Therefore, both strategies are standard together in commercial processes. Verification / Alternative check: Industrial case studies for monosodium glutamate and lysine report improved titers after combining deregulated enzymes with export systems or controlled permeability changes. Why Other Options Are Wrong: Regulatory mutants only: improves production but may still be limited by export. Permeability only: without overproduction, secretion gains are modest. None of the above: inconsistent with well-established practice. Common Pitfalls: Over-leakage can harm growth; optimization balances cell health with secretion. Also, uncontrolled mutations may hurt stability; robust strains use targeted edits. Final Answer: Both (a) and (b)

Question 6

Citric acid manufacturing: What fermentation modes are commonly used to obtain citric acid as a fermentation product?

Accepted Answer

Introduction / Context: Citric acid is one of the world’s highest-volume organic acids. It is produced microbially, classically by Aspergillus niger, using processes designed to drive carbon flux through the tricarboxylic acid pathway and to secrete citrate at high yields. Given Data / Assumptions: Organism: typically Aspergillus niger. Industrial goal: high titer, high yield, and efficient downstream recovery. Common fermentation configurations include submerged aerated and surface (tray) processes. Concept / Approach: Submerged aerated fermentation uses stirred-tank or bubble-column reactors with strong aeration and controlled pH, nutrients, and trace metals to favor citrate overflow. Surface (stationary tray) fermentation spreads the culture on shallow trays to foster high oxygen transfer at the air–solid interface. Historically, both methods have been used; modern plants favor submerged aerated for scalability and control, but surface methods remain instructive and sometimes economical. Step-by-Step Solution: Identify the two main historical/industrial methods for citric acid.Recognize that both submerged aerated and stationary tray processes deliver oxygen and carbon sources to A. niger.Acknowledge that both are “commonly used,” with differing economics and control.Hence select the combined option. Verification / Alternative check: Process histories show transitions from surface to submerged methods as engineering controls improved; nevertheless, both are recognized production routes. Why Other Options Are Wrong: Only submerged or only tray: each alone is incomplete. None of these: contradicts standard industrial practice. Common Pitfalls: Confusing “surface” with “solid-state” only; tray processes often involve moist solid substrates with high oxygen exposure. Final Answer: Both (a) and (b)

Question 7

History of antibiotics: Who first observed and reported the antibiotic and therapeutic properties of penicillin?

Accepted Answer

Introduction / Context: Understanding who first recognized penicillin’s antibacterial action is foundational to the history of antibiotics. Penicillin opened the modern era of antimicrobial chemotherapy and transformed clinical medicine. Given Data / Assumptions: The question asks for the first observation and report of penicillin’s antibiotic properties. We distinguish discovery/observation from later isolation, purification, and development. Concept / Approach: In 1928, Alexander Fleming noticed that a Penicillium mold contaminant inhibited Staphylococcus bacterial growth on an agar plate. He described the antibacterial substance “penicillin” and its therapeutic potential, though large-scale production and clinical deployment came later through the work of Florey, Chain, and colleagues. Step-by-Step Solution: Recall the timeline: 1928 observation and 1929 publication by A. Fleming.Identify contributions: Florey and Chain later purified and mass-produced; Abraham contributed to characterizing penicillin.Pasteur predates antibiotics; his work laid microbiology foundations, not penicillin discovery.Therefore select “Alexander Fleming.” Verification / Alternative check: Standard medical histories credit Fleming with the initial observation; Nobel Prize in 1945 was awarded to Fleming, Florey, and Chain for penicillin. Why Other Options Are Wrong: E. P. Abraham: helped elucidate penicillin chemistry but was not the first observer. Louis Pasteur: pioneered germ theory, vaccines, and fermentation science, not penicillin. S. C. Prescott: known for food science and microbiology texts, not penicillin’s discovery. Common Pitfalls: Confusing discovery (Fleming) with development (Florey & Chain) or later chemical characterization. Final Answer: Alexander Fleming

Question 8

Enzyme sources in industry: Amyloglucosidase (glucoamylase) used for starch-to-glucose conversion is produced by which organism(s)?

Accepted Answer

Introduction / Context: Amyloglucosidase (also called glucoamylase) is a key saccharifying enzyme for converting liquefied starch into glucose syrups, high-glucose feeds for isomerization to high-fructose syrups, and other sweeteners. Multiple fungi are known industrial sources. Given Data / Assumptions: The question lists Rhizopus niveus and Endomycopsis fibuliger among options. Industry widely uses fungal glucoamylases due to suitable pH/temperature profiles and secretion capacity. Concept / Approach: Species in Rhizopus and Endomycopsis (now often reclassified taxonomically) are classic producers of amyloglucosidase, along with Aspergillus species. Both R. niveus and E. fibuliger have been reported to yield active glucoamylase preparations used in starch processing. Therefore, the combined option is correct. Step-by-Step Solution: Identify organisms known to produce glucoamylase.Confirm that both Rhizopus niveus and Endomycopsis fibuliger are traditional sources.Select the inclusive option that names both organisms.Exclude organisms without strong association for this specific enzyme in industry. Verification / Alternative check: Process literature and enzyme catalogs list Rhizopus and Endomycopsis-derived amyloglucosidases for saccharification steps. Why Other Options Are Wrong: Rhizopus niveus only or Endomycopsis only: incomplete. Sclerotina libertina: not a standard industrial source of glucoamylase for starch saccharification. Common Pitfalls: Conflating alpha-amylase (liquefaction) with amyloglucosidase (saccharification); both are used but produced by different strains and conditions. Final Answer: Both (a) and (b)

Question 9

Antibiotics: Neomycin B is produced by which Streptomyces species?

Accepted Answer

Introduction / Context: Neomycin is an aminoglycoside antibiotic complex (notably neomycin B and C) used topically and in some oral applications. Knowing the producing organism guides both historical understanding and strain selection for industrial processes. Given Data / Assumptions: Question targets the species associated with neomycin B. We differentiate among several Streptomyces producing different aminoglycosides. Concept / Approach: The classic producer of neomycin B (and C) is Streptomyces fradiae. Other species listed are known for different products: for example, S. griseus famously produces streptomycin. Correct identification relies on matching antibiotic families with their canonical producing strains. Step-by-Step Solution: List antibiotics associated with each Streptomyces species.Recall neomycin linkage to S. fradiae from industrial microbiology references.Select S. fradiae accordingly.Exclude species tied to other antibiotic families. Verification / Alternative check: Pharmacognosy and fermentation process sources document neomycin biosynthesis in S. fradiae, including gene clusters for aminoglycoside assembly. Why Other Options Are Wrong: Streptomyces griseus: producer of streptomycin, not neomycin B. Streptomyces spheroides / Streptomyces niveus: associated with other metabolites; not the classic neomycin B source. Common Pitfalls: Confusing aminoglycoside producers because multiple Streptomyces make related compounds; pay attention to the specific molecule. Final Answer: Streptomyces fradiae

Question 10

History of fermentation science: Who first identified the chemical that causes the souring of milk (lactic acid)?

Accepted Answer

Introduction / Context: Lactic acid is the key organic acid responsible for the sour taste of fermented milk products. Distinguishing who discovered the acid itself versus who explained the biological mechanism of lactic fermentation is a classic history-of-science question. Given Data / Assumptions: The question asks about the chemical (lactic acid), not the microbial mechanism. Multiple historical figures contributed to fermentation science in different ways. Concept / Approach: Carl Wilhelm Scheele (often cited simply as Scheele) isolated and described lactic acid in the 18th century from sour milk. Decades later, Louis Pasteur elucidated that lactic acid fermentation is a biological process carried out by microorganisms, establishing the role of lactic acid bacteria. The distinction is between chemical discovery and microbiological explanation. Step-by-Step Solution: Identify the target: discovery of the acid that sours milk.Recall Scheele’s isolation of lactic acid from sour milk.Recognize Pasteur’s later role in proving fermentation is biological, not spontaneous chemical change.Therefore, the correct choice is Scheele. Verification / Alternative check: Chemistry histories record Scheele’s many acid discoveries (e.g., oxalic, lactic), predating Pasteur’s microbiology era. Why Other Options Are Wrong: Pasteur: established microbial causation of fermentation, not the first to discover lactic acid. Ronald Ross: known for demonstrating malaria parasite transmission by mosquitoes. Watson: associated with DNA structure (with Crick), unrelated to lactic acid discovery. Common Pitfalls: Conflating discovery of a compound with later elucidation of its biogenesis. Final Answer: Scheele

Question 11

Industrial enzymes: Glucose oxidase used to remove glucose from egg products before drying is typically produced by submerged aerated fermentation using which microorganism?

Accepted Answer

Introduction / Context: Glucose oxidase is used in the food industry to remove residual glucose from egg white and whole eggs prior to drying, reducing Maillard browning and improving shelf stability. Knowing the industrial source organism is essential for process selection and regulatory considerations. Given Data / Assumptions: Target enzyme: glucose oxidase (GOx). Application: deglucosylation of egg products prior to spray drying. Process mode: submerged aerated fermentation. Concept / Approach: Aspergillus niger is the classic industrial producer of glucose oxidase. The fungus secretes GOx extracellularly, enabling efficient recovery. While other microbes may produce oxidases, A. niger remains the principal commercial source due to high yields, established fermentation know-how, and Generally Recognized As Safe (GRAS) status for enzyme preparations. Step-by-Step Solution: Identify the enzyme–organism pairing widely used in industry.Recall A. niger’s secretion of carbohydrate-active enzymes including GOx.Note that submerged aerated fermentation supports high oxygen transfer required for oxidase production.Select A. niger as the correct choice. Verification / Alternative check: Enzyme supplier catalogs and food processing literature consistently cite A. niger–derived GOx for egg and baking applications. Why Other Options Are Wrong: B. subtilis / B. cereus: not standard sources for commercial GOx used in egg processing. A. flavus: associated with aflatoxin risk; not preferred for food enzyme production. Common Pitfalls: Confusing glucose oxidase with glucose dehydrogenase; the latter has different cofactors and applications. Final Answer: A. niger

Question 12

Beta-lactam biosynthesis: Which precursor feeds are used to produce the side chain of Penicillin G in industrial fermentation?

Accepted Answer

Introduction / Context: In industrial beta-lactam production, the side chain of penicillins can be directed by adding precursor molecules to the fermentation. Matching the correct precursor to the desired penicillin is essential for product specificity. Given Data / Assumptions: Penicillin G is benzylpenicillin. The benzyl side chain is derived from an aromatic acid precursor. Different precursors yield different penicillins (e.g., V vs. G). Concept / Approach: For Penicillin G, the side chain is benzyl (phenylmethyl). Feeding phenylacetic acid to Penicillium fermentation directs acyltransfer to form benzylpenicillin. In contrast, feeding phenoxyacetic acid leads to Penicillin V (phenoxymethylpenicillin). Step-by-Step Solution: Identify the target penicillin: Penicillin G (benzylpenicillin).Match benzyl side chain with phenylacetic acid as precursor.Exclude phenoxyacetic acid, which corresponds to Penicillin V.Select phenylacetic acid as correct. Verification / Alternative check: Process manuals for penicillin fermentation describe precursor feeding strategies to direct side-chain composition, including phenylacetic acid for G. Why Other Options Are Wrong: Phenoxy acetic acid: used for Penicillin V, not G. Hydroxy phenyl acetic acid: not the standard industrial precursor for Penicillin G. None of these: incorrect because phenylacetic acid is correct. Common Pitfalls: Confusing “phenyl” and “phenoxy” leads to mixing up G and V variants. Final Answer: Phenyl acetic acid

Question 13

Biocontrol: Bacillus thuringiensis (Bt) is commercially used primarily as which type of agricultural input?

Accepted Answer

Introduction / Context: Bacillus thuringiensis (Bt) is a soil bacterium that produces crystal (Cry) and Cyt toxins effective against specific insect larvae. Bt-based products are mainstays of integrated pest management and have also informed genetically engineered crops expressing Bt toxins. Given Data / Assumptions: Bt forms parasporal crystal proteins during sporulation. These proteins are insecticidal upon activation in alkaline insect midguts. Commercial formulations deliver spores and crystals to target pests. Concept / Approach: Because Bt targets insects (e.g., Lepidoptera, Coleoptera) at specific life stages, it is categorized and sold as a microbial pesticide (more precisely, an insecticide). It is not used as an herbicide, vitamin producer, or antibiotic source in standard agricultural practice. Step-by-Step Solution: Identify Bt’s active principle: Cry/Cyt proteins toxic to insects.Map application: control of caterpillars, beetle larvae, and mosquitoes depending on toxin type.Conclude that the correct agricultural role is pesticide.Rule out unrelated categories (herbicide, vitamins, antibiotics). Verification / Alternative check: Regulatory agencies list Bt products as biopesticides; product labels specify insect targets and application rates. Why Other Options Are Wrong: Source of antibiotics: Bt is not a commercial antibiotic source. Herbicide: Bt toxins do not target plants; they target insects. Producer of vitamins: not the commercial purpose of Bt preparations. Common Pitfalls: Assuming all microbial agricultural inputs are fertilizers or plant growth promoters; Bt is squarely an insecticidal biocontrol agent. Final Answer: Pesticide

Question 14

Penicillins vs. non-penicillins: Which of the following is NOT a penicillin-class antibiotic (choose the non-penicillin)?

Accepted Answer

Introduction / Context: Beta-lactam antibiotics include several subclasses with related mechanisms but distinct core structures: penicillins, cephalosporins, carbapenems, and monobactams. Distinguishing penicillins from non-penicillins is a foundational pharmacy and microbiology skill. Given Data / Assumptions (Recovery Note): The original options included ambiguous names (e.g., “Penicillin X/Y”), which are not standard in clinical use. Applying the Recovery-First Policy, we reconstruct realistic choices while preserving the intended concept: identify a non-penicillin among common antibiotics. We include two canonical penicillins (G and V) and a widely used aminopenicillin (ampicillin) alongside a cephalosporin (cephalexin). Concept / Approach: Penicillins share a beta-lactam fused to a thiazolidine ring (penam nucleus). Cephalosporins have a beta-lactam fused to a dihydrothiazine ring (cephem nucleus). While both inhibit transpeptidases involved in peptidoglycan synthesis, they are distinct classes. Step-by-Step Solution: List each option and its class: Penicillin G (benzylpenicillin), Penicillin V (phenoxymethylpenicillin), Ampicillin (aminopenicillin), Cephalexin (first-generation cephalosporin).Identify the one that is not a penicillin: cephalexin is a cephalosporin.Therefore select “Cephalexin.”Confirm that the remaining options are penicillins. Verification / Alternative check: Drug references classify cephalexin under cephalosporins; penicillin G/V and ampicillin are well-known penicillins. Why Other Options Are Wrong: Penicillin G: a natural penicillin used parenterally. Penicillin V: an orally stable natural penicillin. Ampicillin: a semisynthetic penicillin with broader Gram-negative activity. Common Pitfalls: Assuming all beta-lactams are “penicillins”; class matters for spectrum, stability, and allergy cross-reactivity. Final Answer: Cephalexin

Question 15

In industrial and food biochemistry, the enzyme “invertase” catalyzes the hydrolysis of sucrose to glucose and fructose. What is the commonly used alternative name for invertase?

Accepted Answer

Introduction / Context: Invertase is a widely used industrial enzyme in confectionery, beverage, and baking applications. It hydrolyzes the disaccharide sucrose into the monosaccharides glucose and fructose, a mixture commonly called “invert sugar.” Because enzyme naming can vary between fields and eras, this question checks your ability to recognize established synonyms used across biochemistry and food technology. Given Data / Assumptions: The enzyme in question catalyzes sucrose → glucose + fructose. “Other name” refers to well-accepted synonyms in textbooks and industrial practice. Only one option should capture the complete set of correct synonyms provided. Concept / Approach: Historically, enzymes that act on sucrose have been named either for the substrate (sucrose) or for traditional terminology in sugar chemistry. Hence, “sucrase” directly references the substrate sucrose, while “saccharase” derives from “sacchar-,” a root meaning sugar. Both terms are used interchangeably for invertase in many references, particularly in food science contexts. Step-by-Step Solution: Identify the reaction: sucrose hydrolysis producing invert sugar.Match standard synonyms: “sucrase” and “saccharase” both denote invertase.Exclude unrelated enzyme classes such as “isomerase,” which rearrange molecules rather than hydrolyze glycosidic bonds.Select the combined answer that includes both synonyms. Verification / Alternative check: Food and brewing literature commonly cites invertase as sucrase/saccharase. Enzyme Commission naming places invertase under EC 3.2.1.26 (beta-fructofuranosidase); despite the systematic name, the common synonyms remain in active use. Why Other Options Are Wrong: “Sucrase” alone or “saccharase” alone is incomplete if both are accepted synonyms. “Isomerase” is an incorrect class for this hydrolytic reaction. Common Pitfalls: Assuming only one synonym is correct; overlooking that common names persist alongside systematic EC names. Final Answer: both (a) and (b)

Question 16

A milestone in amino-acid biotechnology: The first large-scale commercial process used to produce L-lysine by microorganisms is commonly referred to as which type of fermentation process?

Accepted Answer

Introduction / Context: L-lysine is an essential amino acid widely produced for feed supplementation and food applications. Early commercial biotechnological routes shifted from chemical synthesis to microbial production using selected and improved strains. This question targets the terminology used to describe that pioneering large-scale bioprocess. Given Data / Assumptions: The focus is on the first commercial microbial process for L-lysine. Industrial practice adopted specific labels for routes that used one organism in a single step versus more complex or staged approaches. Terminology distinguishes “direct” microbial fermentation from chemical or multistep hybrid routes. Concept / Approach: “Direct fermentation” describes the microbial conversion of carbohydrate feedstocks into L-lysine in a single bioreactor pathway using improved bacteria (for example, coryneform bacteria). This contrasts with terms like “dual” or “indirect,” which imply multi-stage, coupled, or non-purely microbial routes. Historically, direct fermentation became the foundation for the modern L-lysine industry. Step-by-Step Solution: Recall industrial shift: chemical → microbial for cost and sustainability.Associate first commercial success with one-step microbial bioprocess.Identify this route’s canonical name as “direct fermentation.” Verification / Alternative check: Process descriptions from the amino-acid industry document direct fermentation using carbohydrate substrates, aerated tanks, and strain improvement to maximize yields. Why Other Options Are Wrong: “Dual” or “indirect” fermentation do not denote the historically accepted one-step microbial route and are not standard names for the original process. A combined answer cannot be correct because only one term is historically canonical. Common Pitfalls: Confusing generic “multi-step processing” with named fermentation categories; assuming the earliest processes were hybrid when, in fact, direct fermentation soon dominated. Final Answer: direct fermentation

Question 17

Microbial producers for L-lysine (direct method): Which organism/strain type is classically employed for the commercial “direct fermentation” of L-lysine?

Accepted Answer

Introduction / Context: L-lysine production is a hallmark of industrial microbiology. It relies on aerobic, high-cell-density fermentation with robust producers from the coryneform group. Historically, nomenclature has changed (e.g., Micrococcus glutamicus is an older name; Corynebacterium glutamicum is widely used now), but the concept of using improved (mutated/selected) strains remains central. Given Data / Assumptions: “Direct method” refers to single-organism microbial fermentation from sugars to L-lysine. Industrial processes typically deploy improved or mutated strains to remove feedback inhibition and increase flux toward lysine biosynthesis. Legacy organism names appear in classic exam options. Concept / Approach: Among traditional exam answers, the mutated strain of Micrococcus glutamicus (now recognized as Corynebacterium glutamicum) is most closely associated with commercial lysine production by direct fermentation. While other coryneform bacteria (e.g., Brevibacterium spp.) are also used, the best single match to the phrasing “direct method” in classic references is the improved strain of Micrococcus/Corynebacterium. Step-by-Step Solution: Map “direct fermentation” to coryneform bacteria used at scale.Recognize naming conventions: Micrococcus glutamicus ≈ Corynebacterium glutamicum in older literature.Choose the option specifying an improved/mutated strain to reflect industrial practice. Verification / Alternative check: Process patents and textbooks consistently cite improved coryneform strains (e.g., auxotrophs or deregulated mutants) for high-yield L-lysine production. Why Other Options Are Wrong: Wild-type strains (without improvement) are typically insufficient for industrial titers. Other species listed have been explored, but the most classical answer for direct L-lysine fermentation is the mutated Micrococcus/Corynebacterium lineage. Common Pitfalls: Overlooking historical names or assuming only one genus is ever used; multiple genera exist, but exam conventions favor the coryneform prototype. Final Answer: Mutated strain of Micrococcus glutamicus

Question 18

History of antibiotics manufacturing: Penicillin was first produced commercially at scale using which bioprocess configuration?

Accepted Answer

Introduction / Context: The World War II era catalyzed the transition of penicillin from a laboratory curiosity to a mass-produced, life-saving antibiotic. Understanding the production method highlights the importance of bioreactor design, oxygen transfer, and aseptic scale-up in industrial biotechnology. Given Data / Assumptions: Penicillin is produced by filamentous fungi (e.g., Penicillium, later Penicillium/Aspergillus strains). High oxygen demand requires efficient aeration and agitation. “First produced commercially” refers to the breakthrough process used to meet war-time demand. Concept / Approach: Early work used surface (stationary) cultures, but these could not meet volume and oxygenation needs. The decisive advance was deep-tank, aerated, and agitated fermentation, enabling high dissolved oxygen and consistent sterility at scale. This process innovation made penicillin widely available and set templates for modern antibiotic fermentations. Step-by-Step Solution: Eliminate “stationary mat” for insufficient O2 transfer and scalability.Recognize deep tank + aeration + agitation as the historical breakthrough.Note that continuous fermentation was not the initial commercial mode for penicillin.Select “deep tank aerated fermentations.” Verification / Alternative check: Historical accounts from WWII production document the adoption of deep-tank technology (sterile air sparging, mechanical agitation) to achieve industrial titers. Why Other Options Are Wrong: Surface culture was used early but not for “first commercial at scale.” Continuous fermentation is not the canonical initial method for penicillin. Common Pitfalls: Conflating early lab-scale surface cultures with the industrial breakthrough; assuming continuous mode was standard for early antibiotics. Final Answer: deep tank aerated fermentations

Question 19

Brewing science – malting step: How is the malt used to ferment beer prepared from barley before mashing?

Accepted Answer

Introduction / Context: Malting is a critical pre-fermentation step in brewing that activates grain enzymes, particularly amylases, which later convert starches to fermentable sugars during mashing. Understanding malting clarifies how raw barley becomes a suitable substrate for yeast fermentation. Given Data / Assumptions: Barley is the standard malting grain. Germination develops endogenous enzyme systems. Drying (kilning) stops germination while preserving enzyme activity profiles suited to beer style. Concept / Approach: The classical malting sequence is steeping (soaking), germination, and kilning (controlled drying). Steeping raises moisture, germination triggers enzyme synthesis and modification of endosperm, and kilning halts growth while setting color and flavor precursors. This process is distinct from simple washing or exogenous enzyme addition. Step-by-Step Solution: Identify malting goals: enzyme activation and endosperm modification.Recall the canonical steps: soak → germinate → dry (kiln).Select the option that captures all three elements in sequence. Verification / Alternative check: Brewing texts specify steeping to about 42–46% grain moisture, germination under controlled conditions, then kilning to achieve the target malt profile. Why Other Options Are Wrong: Roasting alone does not create malt; washing and air-drying do not induce germination; adding bovine amylase is not standard malting practice and ignores endogenous enzyme development. Common Pitfalls: Confusing roasting (used for specialty malts) with the entire malting process; underestimating germination’s role in enzyme formation. Final Answer: soaking barley in water followed by germination and drying

Question 20

Industrial biopolymers from microbes: Most commercially targeted and secreted macromolecules produced by microorganisms belong to which category?

Accepted Answer

Introduction / Context: Microorganisms synthesize a variety of macromolecules, but industrial biotechnology focuses on those that can be secreted, recovered, and used at scale. Recognizing which class dominates commercial applications helps frame downstream processing and market uses. Given Data / Assumptions: Target is “produced by microorganisms” with emphasis on recoverable products. Industrial examples include xanthan, gellan, dextran, pullulan, alginate (bacterial/biotech sources). Products should be practical for use in food, pharma, oilfield, and materials applications. Concept / Approach: Exopolysaccharides (EPS) are extracellular polymers secreted into the medium, simplifying harvest compared with intracellular components. They exhibit valuable rheological properties (viscosity, gelation), biofilm formation capabilities, and functional attributes exploited in thickening, stabilizing, and encapsulation. While cell wall polymers exist, they are not typically recovered as primary commercial products; nucleic acids and histones are not mainstream industrial polymer products. Step-by-Step Solution: List prominent microbial polymer products: xanthan (Xanthomonas), gellan (Sphingomonas), dextran (Leuconostoc).Note that these are excreted and readily recovered from broth.Select “exopolysaccharides” as the dominant industrial category. Verification / Alternative check: Commercial datasheets and approvals (e.g., food additive codes) heavily feature microbial EPS as thickeners and stabilizers. Why Other Options Are Wrong: Cell wall constituents are structural and not commonly targeted as purified products; nucleic acids/histones are specialty biomolecules with limited bulk applications. Common Pitfalls: Confusing general cellular polymers with secreted, harvestable industrial products. Final Answer: exopolysaccharides

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