Q.16 The specific productivity (qp) of cellulase production by Aspergillus niger follows a linear relationship with the specific growth rate (μ) and is of the form qp = αμ + β, where α and β are constants. Assuming that the values of α and β are 0.006 and 25, respectively, which type of product formation kinetics is TRUE?
(A) Growth-dependent kinetics
(B) Non-growth-dependent kinetics
(C) Both growth- and non-growth-dependent kinetics
(D) Inhibition kinetics
The specific productivity (qp) of cellulase production by Aspergillus niger follows qp = 0.006μ + 25, indicating mixed kinetics where product formation depends on both growth rate and non-growth factors.
This linear equation matches the Leudeking-Piret model, qp = αμ + β, with both coefficients non-zero.
Option Analysis
Growth-dependent kinetics applies when qp = αμ (β = 0), so product forms strictly with growth, as in primary metabolites. Here β = 25 ≠ 0, so incorrect.
Non-growth-dependent kinetics occurs when qp = β (α = 0), typical for secondary metabolites in stationary phase. α = 0.006 ≠ 0 rules this out.
Both growth- and non-growth-dependent kinetics fits since α > 0 links to growth and β > 0 allows production without growth. Correct answer: (C).
Inhibition kinetics involves substrate/product reducing rates (e.g., Haldane model), unrelated to this growth-product link. Incorrect.
Introduction: Specific Productivity Cellulase Production Aspergillus Niger qp = αμ + β
Specific productivity (qp) measures product formation rate per biomass unit in microbial fermentations like cellulase production by Aspergillus niger. The equation qp = αμ + β, with α=0.006 and β=25, reveals mixed product formation kinetics crucial for bioprocess optimization in exams like CSIR NET Life Sciences.
Leudeking-Piret Model Explained
The Leudeking-Piret equation, dPdt=αdXdt+βX or specific form qp=αμ+β, describes:
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α term: Growth-associated (primary metabolites like ethanol).
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β term: Non-growth-associated (secondary like antibiotics).
Both non-zero values confirm mixed kinetics for cellulase.
Implications for Aspergillus niger Cellulase
Aspergillus niger produces cellulase via solid/submerged fermentation. The positive α shows growth boosts qp slightly, while high β=25 dominates at low μ, enabling production in stationary phase. Optimize via chemostat for max qp near half-maximal μ.
| Kinetics Type | Equation Form | α Value | β Value | Example |
|---|---|---|---|---|
| Growth-dependent | qp = αμ | >0 | 0 | Amino acids |
| Non-growth | qp = β | 0 | >0 | Penicillin |
| Mixed | qp = αμ + β | >0 | >0 | Cellulase here |
| Inhibition | qp decreases with substrate | N/A | N/A | None |
