engleski

Lipase production from Thermomyces lanuginosus: optimization and scale-up of the bioprocess

The first part of the research aimed to determine optimal process conditions for Thermomyces lanuginosus lipase (TLL) production during solid- state fermentation (SSF) in the laboratory jars on hull-less pumpkin oil pomace as a substrate. Inoculation of the substrate was performed with mycelium discs (nMD) (Ø = 1 cm) of T. lanuginosus suspended in distilled and sterile water. Numerical optimization of the five independent variables, which affected the TLL production, was evaluated using response surface methodology according to the Box-Behnken experimental plan. To predict the TLL production, reduced quadratic mathematical model was proposed and model validation was performed under optimized conditions (ms = 50 g, nMD = 7, wH2O = 60 %, t = 2 days, T = 45 °C) with 95 % accuracy. The maximum TLL activity was 162 U g-1db. After SSF process optimization in the laboratory jars, the scale-up of the process was investigated in a tray bioreactor. To find out the best methodology to produce inoculum (fungal mycelia) to start up the lipase production process in a tray bioreactor, various substrates (pumpkin oil pomace, sugar beet pulp, barley husk, and spelt husk) were tested. Therefore, 250 g of oil pomace was mixed with 350 mL distilled water, sterilized, cooled down, and inoculated with mycelia produced on previously mentioned substrates. The initial concentration of the inoculum in all experiments was 25-30 % (w/w). The highest volumetric activity of the lipase was observed with sugar beet pulp used for inoculum production. The initial substrate mass was scaled up to full tray bioreactor capacity, as follows: 1062.5 g of pumpkin pomace mixed with 1487.5 mL distilled water and inoculated with 605 g of mycelium proliferated on the sugar beet pulp. The highest TLL activity (400 U g-1db) was measured after 3rd day of SSF which was 2.5-fold higher compared to experiments performed in laboratory jars.

lipase ; Thermomyces lanuginosus ; solid-state fermentation ; response surface methodology ; tray bioreactor

nije evidentirano