Rice husk as a source for fungal biopesticide production by solid-state fermentation using B. bassiana and T. harzianum

Solid-state fermentation using rice husk as substrate with either Beauveria bassiana or Trichoderma harzianum was conducted on batch reactors at laboratory scale to establish optimal conditions for spore production. Time course tests were performed to determine maximum spore production time, which was 7.7 days for Beauveria bassiana and 5.7 days for Trichoderma harzianum. The effect of moisture, inoculum concentration, airflow rate, temperature and C/N ratio on spore production was evaluated by two Box-Behnken experimental designs. Final spore concentrations ranged from 2.0x10(8) to 2.0x10(9) spores g(-1) dry matter. Main factors influencing spore production were moisture (optimum values of 55-60% for Trichoderma harzianum and 65-70 for Beauveria bassiana) and temperature (25 degrees C). The effect of mixing enhanced Trichoderma harzianum spore production while influencing negatively in the case of Beauveria bassiana. Robustness of the process has been demonstrated through statistical analysis using box-plots.