Mustard oil cake (Brassica napus), the residue obtained after extraction of mustard oil from mustard oil seeds, was investigated for the production of lipase under solid state fermentation (SSF) using the marine yeast Yarrowia lipolytica NCIM 3589. Process parameters such as incubation time, biomass concentration, initial moisture content, carbon source concentration and nitrogen source concentration of the medium were optimized. Screening of ten nitrogen and five carbon sources has been accomplished with the help of Plackett-Burman design. The highest lipase activity of 57.89 units per gram of dry fermented substrate (U/gds) was observed with the substrate of mustard oil cake in four days of fermentation.

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The purpose of the present investigation is to enhance production of the biomedically important enzyme, lipase, by subjecting the indigenous lipase producing fungal strain Aspergillus japonicus MTCC 1975 to strain improvement and random mutagenesis (UV irradiation, HNO 2 and N-methyl-N'nitro-N-nitroso guanidine). The isolation of mutants and the lipolytic activity of selected mutants were described. The best UV selectant (AUV 3) showed 127% higher lipase activity than the parent strain. The lipase yield of the best HNO 2 mutant (AHN 3) was 139% higher than UV mutant (AUV 3) and 177% higher than the parent strain. Also, the lipase yield of the best NTG mutant (ANT 4) was 156% higher lipase activity than the HNO 2 mutant (AHN 3) and 217% higher than the UV mutant (AUV 3) and 276% higher lipase activity than the parent strain. The results indicated that UV, HNO 2 and NTG treatment were effective physical and chemical mutagenic agents for strain improvement of Aspergillus japonicus for enhanced lipase productivity.

This research work has been carried out to establish the combinatorial impact of various fermentation medium constituents, used for poly‐β hydroxybutyrate (PHB) biosynthesis. Model development was performed with an optimized medium composition that enhanced the biosynthesis of PHB from the biowaste material Brewers’ spent grain (BSG). The latter was used as a carbon substrate in submerged fermentation with Bacillus sphaericus NCIM 2478. Three independent variables: BSG, yeast extract (YE), and salt solution concentration (SS) and one dependent variable (amount of PHB produced) were assigned. A total of 35 microbial fermentation trials were conducted by which a nonlinear mathematical relationship was established in terms of neural network model between independent and dependent variables. The resulting artificial neural networks (ANNs) model for this process was further optimized using a global genetic algorithm optimization technique, which predicted the maximum production of PHB (916.31 mg/L) at a concentration of BSG (50.12 g/L), concentration of YE (0.22 g/L), and concentration of SS (24.06%, v/v). The experimental value of the quantity of PHB (concentration ∼916 mg/L) was found to be very close to the value predicted by the ANN–GA model approach.

Doehlert experimental design (DD) was applied for the optimization of medium constituents for L-asparaginase production by Yarrowia lipolytica NCIM 3472 in solid state fermentation (SSF) using palm kernel cake as the substrate. From the results of preliminary experimental runs, the three variables (glucose, moisture content, L-asparagine) have been identified as the potential variables for the production of L-asparaginase. Fifteen experimental runs designed by DD are carried out and the process response is modeled using a polynomial equation as function of these parameters. The proposed quadratic model for DD fitted very well to the experimental data that it could be used to navigate the design space according to analysis of variance results. The experimental values were in good agreement with predicted values and the correlation coefficient was found to be 0.9988. The optimal set of conditions for maximum L-asparaginase activity was as follows: moisture content of the substrate: 54.8622 (%), glucose concentration: 11.9241 (%w/w) and L-asparagine concentration: 1.0758 (%w/w). L-asparaginase activity at these optimum conditions was 39.8623 U/gds. STATISTICA 6.0 was used for implementing Doehlert experimental design.