CHAPTER 15: Tipula abdominalis: a Natural Biorefinery with Novel Microbial Enzymes Useful for Pectin-Rich Biomass Deconstruction

The Tipula abdominalis larval gut is a model natural biorefinery where maceration decreases the particle size and increases the surface-area-to-volume ratios of biomass substrates. Further pretreatment occurs in the alkaline midgut where proteolysis degrades complexed proteins making polysaccharide polymers more accessible. In the neutral-pH hindgut, bacterial enzymes refine plant polymers into monomeric units. Released sugars are then consumed by bacteria and converted to fermentation products, which can be transported across the gut to the hemolymph to support larval energy and growth requirements. Microorganisms isolated from the T. abdominalis larval hindgut include Paenibacillus amylolyticus. A genomic library from P. amylolyticus 27C64 was screened for various enzyme activities useful in biomass conversions and a novel pectate lyase with unusual activity on both polygalacturonate and highly methylated pectin was discovered. Addition of PelB to pectin-rich fermentations with low commercial enzyme loadings increased ethanol yield.