The use of dung beetle larvae gut microbial consortia in the production of biogas and bio-ethanol

Moyo, Phanankosi
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The goal of this study was to develop a standard and reproducible method for the propagation of Euoniticellus intermedius (Coleoptera: Scarabaeida) larvae gut microbial consortia and subsequently use them in the production of bio-ethanol and biogas. Homogenized midgut and hindgut sections of the larvae were enriched in 4 different media (NB, TSB, M1A and M1B) under oxic conditions for 4 weeks with TSB giving the highest microbial counts with 3 x 107 CFU/ml for the hindgut consortium and 1.9 x 107 CFU/ml for the midgut consortium. M1B enriched microbes gave the lowest counts at 1.1 x 107 CFU/ml and 1.0 x 107 CFU/ml for hindgut and midgut consortium, respectively. Midgut consortium enriched in M1B showed the greatest visible filter paper degradation along with the unenriched midgut consortium from the dung beetle larvae. However, HPLC analysis only detected D-glucose from filter paper degraded by hindgut microbes from TSB (0.34 g/l), midgut microbes from M1B (0.03 g/l) and hindgut microbes from the dung beetle (0.09 g/l). Ethanol detected from the experimental runs could not be conclusively attributed to gut consortia metabolic activity. Methane production was detected from the cultures incubated anaerobically for 8 weeks. The hindgut consortium consistently gave the highest concentration of methane with an average of 0.034 moles/l of methane produced from medium AM1 (carbon sources were D-glucose and D-lactose). Automated ribosomal RNA intergenic spacer analysis (ARISA) showed a clear distinction between the bacterial communities found in the midgut and hindgut of E. intermedius third instar larvae.