Response surface methodology for lovastatin production by Aspergillus terreus GD13 strain

A wild type Aspergillus terreus GD13 strain, chosen after extensive screening, was optimized for lovastatin production using statistical Box-Behnken design of experiments. The interactive effect of four process parameters, i.e. lactose and soybean meal, inoculum size (spore concentration) and age of the spore culture, on the production of lovastatin was evaluated employing response surface methodology (RSM). The model highlighted the positive effect of soybean meal concentration and inoculum level for achieving maximal level of lovastatin (1342 mg/l). The optimal fermentation conditions improved the lovastatin titre by 7.0-folds when compared to the titres obtained under unoptimized conditions

Generating Fermentable Sugars from Rice Straw Using Functionally Active Cellulolytic Enzymes from <i>Aspergillus niger</i> HO

Among the three <i>Aspergillus</i> spp. (<i>A. niger</i>, <i>A. oryzae</i>, and <i>A. fumigatus</i>) screened for cellulolytic enzyme production potential, <i>A. niger</i> produced cellulolytic enzyme in relatively higher concentrations than the other two isolates. Enzyme produced by all three isolates was optimally active at pH 5.0. Cellulases from <i>A. niger</i> and <i>A. fumigatus</i> were optimally active at 55 °C, while the enzyme from <i>A. oryzae</i> showed optimum activity at 50 °C. Cellulase from <i>A. niger</i> and <i>A. fumigatus</i> retained more than 80 and 70% activity, respectively, while cellulase from <i>A. oryzae</i> could retain only 20% activity at 55 °C after 12 h. Cellulase from <i>A. niger</i> exhibited better stability at higher temperatures than the enzyme from the other two <i>Aspergillus</i> spp., showing half-life (<i>t</i>_1/2) of about 5 and 3 h at 70 and 80 °C, respectively. Zymogram revealed multiple forms of endoglucanase, cellobiohydrolase, and β-glucosidase with molecular mass ranging between 28 and 154 kDa for cellulase from all three isolates. Hydrolysis of rice straw at 12.5% (w/v) with crude cellulase from <i>A. niger</i> HO resulted in fermentable sugar concentration and productivity of 66.2 g L^–1 and 2.75 g L^–1 h^–1, respectively, showing potential for the reported enzyme in biofuel industry