Response surface modeling of factors influencing the production of glucanolytic enzyme complex by Trichoderma harzianum Rifai in bioreactor

Purpose: The objective of this work was to optimize the production of b-1,3-glucanases by Trichoderma harzianum Rifai grown on botryosphaeran (EPS) as sole carbon source under several culture conditions in bioreactor, using factorial design and analysis by response-surface.
Methods: T. harzianum conidia were used to inoculate Erlenmeyer flasks containing liquid medium comprising Vogel minimal salts medium (VMSM) and glucose (10 g/l) as the sole carbon source. After 3 days at 28°C and 180 rpm, the biomass was used to inoculate a 2.4 l bioreactor containing VMSM and EPS (1.5 g/l). To evaluate optimal conditions for the production of b-1,3-glucanases (Y₁) by T. harzianum, the fungal isolate was grown at different aeration rates (x₁); initial pH (x₂) and time of cultures (x₃) according to the experimental design. b-1,3-Glucanase was assayed against laminarin and botryosphaeran (b-1,3;1,6-glucan) as substrates.
Results: According to the results, the variable more important for b-1,3-glucanase production by T. harzianum was initial pH, followed by time of culture. The analysis of variance (ANOVA) showed that the lack-of-fit (p>0.05) was not significant, indicating that the model was predictive. Highest b-1,3-glucanase titres (3.7 U/ml) were obtained at 8 days, initial pH 5.5 and aeration rate of 2 vvm. The R² value implies 97% of the variability in the observed response values can be explained by the model, or by experimental factors and their interactions. The pure error was low, indicating good reproducibility of the experimental data.