Environmental impact of insect rearing for food and feed: state of the art and perspectives

The objective of this study was to examine the effects and role of prebiotics, such as inulin, fructo-oligosaccharides (FOS) and galacto-oligosaccharides (GAS), to mitigate sulfur-containing odour gases, hydrogen sulfide (H2S) and methyl mercaptan (CH3SH) using pigs as in vitro study model. Inocula obtained from pigs were incubated at 39°C for 24 h using 550 mg sterilised substrate (caecal contents supplemented with or without 50 mg prebiotics). Production of total gas, H2S and CH3SH were determined. The results showed that total gas production for the caecal content of pigs was 57.3 mL, and that for H2S and CH3SH was 220.2 and 15.2 ^L, respectively. The total gas production increased (P<0.05), whereas concentrations of H2S and CH3SH decreased (P<0.05) with supplementation of prebiotics. Among the prebiotics, inulin was the most effective in mitigating H2S and CH3SH productions, reducing the two malodorous gases by 14.7 and 19.8%, respectively. The reduction of the above two sulfur-containing gases was supported by lower sulfate-reducing bacteria population and higher sulfate radical concentrations in the prebiotics, particularly that of inulin supplementation group.