In enzymology and food biotechnology, the enzyme β-galactosidase is also known by which commonly used name and formal EC classification?

Introduction:
β-galactosidase is a widely used enzyme in food technology and microbiology. In dairy processing, it is famous for hydrolyzing lactose into glucose and galactose, improving sweetness and digestibility for lactose-intolerant consumers. This question tests recognition of both the common name and the Enzyme Commission (EC) classification that precisely defines its catalytic activity.

Given Data / Assumptions:

• Target enzyme: β-galactosidase.
• Common industrial context: dairy processing and analytics.
• EC numbering follows the Enzyme Commission rules for hydrolases.

Concept / Approach:
The EC system names enzymes based on reaction type. β-galactosidase belongs to hydrolases (EC 3), glycosidases acting on O-glycosyl compounds (EC 3.2), specifically β-galactoside β-galactohydrolases (EC 3.2.1). Its full code EC 3.2.1.23 uniquely identifies its reaction. In dairy, the same enzyme is commonly called lactase because it acts on lactose, a β-galactoside disaccharide.

Step-by-Step Solution:
Step 1: Identify the everyday/industry name. β-galactosidase is colloquially called lactase in milk processing.Step 2: Identify the EC code. Literature and enzyme catalogs list β-galactosidase as EC 3.2.1.23.Step 3: Match with options. Option (a) gives the common name; option (b) gives the EC code; option (c) states both.Step 4: Conclude that both labels refer to the same catalytic entity.

Verification / Alternative check:
Enzyme databanks, dairy processing texts, and microbiology references consistently list lactase/β-galactosidase as EC 3.2.1.23 and describe its role in lactose hydrolysis.

Why Other Options Are Wrong:

• lactase: True but incomplete alone since EC code is also correct.
• EC3.2.1.23: True but incomplete alone; the common name also applies.
• isomerase: Incorrect class; β-galactosidase is a hydrolase, not an isomerase.
• None of these: Incorrect because both (a) and (b) are valid.

Common Pitfalls:
Confusing β-galactosidase (hydrolase) with isomerases that rearrange molecules without hydrolysis; assuming the common name and EC number are mutually exclusive identifiers rather than complementary labels.

Final Answer:
both (a) and (b)