Semi-solid state fermentation of food waste for production of <Emphasis Type="Italic">Bacillus thuringiensis</Emphasis> biopesticide

In this study, Bacillus thuringiensis (Bt) biopesticide was produced through different fermentation processes using food waste with different water contents. The semi-solid state sample with 75% water content presented the highest δ-endotoxin efficiency of 862 μg/mL. δ-endotoxin efficiency increased by 30.2% from that of the solid-state sample (50% water content) and 73.8% from that of the submerged sample (99% water content). Results confirmed that semi-solid state fermentation presents considerable advantages compared with other fermentation types (solid-state and submerged). The timing adjustment of pH and recycling fermentation effectively counteracted the inhibition of pH and product, thereby increasing δ- endotoxin efficiency to 1,648 and 2,478 μg/mL (accumulated value of all four fermentation loops), respectively. A δ- endotoxin slow-release formulation using polylactic acid as the carrier was also developed to effectively promote the stability of Bt biopesticide.