Kinetics and thermodynamics of high level β-glucosidase production by mutant derivative of Aspergillus niger under submerged growth conditions

Abstract

Gamma rays mediated mutagenesis and subsequent selection on 2-deoxy-D-glucose developed a highly catabolite de-repressed and stable β-glucosidase (BGL) hyper-producer mutant of local Aspergillus niger NIBGE, which has high potential for industrial applications. The M6 mutant showed highest constitutive production of BGL (14,900 IU/L) on glucose as compared to control (5,900 IU/L). Wheat bran was the best carbon source and BGL production by parent and mutant strain was 16,200 and 29,500 IU/L, respectively. Effect of inoculum density, pH, temperature and wheat bran concentration on the BGL production was determined in terms of kinetic growth parameters, that is, specific growth rate (), biomass doubling time (t d), product yield coefficient with respect to cell mass (Y p/x) and specific rate of product formation (q p). Optimal conditions for BGL production by parent and mutant strain were same: inoculum level= 0.184 mg cells/mL (10% v/v); optimum temperature= 30°C and pH= 5.0; wheat bran= 3% (w/v). The apparent subunit molecular mass of BGL from both strains was also same (130 kDa). Determination of thermodynamic parameters led to consider that the hyper-production of BGL by the mutant was due to decrease in: activation energy (E a(p)), change in enthalpy (ΔH* (p)) and Gibbs free energy (ΔG* (p)) for product (BGL) formation.

A Sight to Wheat Bran: High Value-Added Products

“…Nagar and others found elevated production of cellulase-poor alkali stable xylanase by Bacillus pumilus SV-85S in the presence of WB under SSF [40]. The enzyme was entirely stable over a wide pH (5)(6)(7)(8)(9)(10)(11) interval and maintained 52% of its efficacy at a temperature of 70 • C for 30 min. Approximate evaluation of price collation showed that the price of the enzyme generation using WB was reduced to 50%.…”

“…Substrate for enzymes production [5] As an inducer for enzymes Complex substrate [9][10][11] Production of protease, amylase, and glucoamylase Nitrogen source [5] Metabolites Bacitracin Cyclosporine-A Gibberellic acid Cheap raw material [12][13][14] Biofuel Bioethanol Biobutanol Biohydrogen…”

“…Enzyme production by solid-state fermentation (SSF) and submerged fermentation (SmF) Substrate for enzymes production [5] As an inducer for enzymes Complex substrate [9][10][11] Production of protease, amylase, and glucoamylase Nitrogen source […”

“…Overall, good yields could be obtained with the general conditions of pH (4)(5)(6)(7)(8)(9)(10)(11), the temperature of 30-70 • C, the cultivation medium should contain glucose, sodium and magnesium salts, fermentation time can vary from 2 till 12 days, substrates combination of WB and soybean can also provide good results.…”