Sugarcane Bagasse Polysaccharides Decomposition by the Cockroach Digestive System

Abstract

Cockroaches are omnivorous insects that consume a diverse diet, including lignocellulose. This study investigated Periplaneta americana, which was fed exclusively on sugarcane bagasse, to evaluate biomass degradation across gut chambers and provide helpful information to the bioenergy industry. We analyzed enzyme activity, the composition of monosaccharides from bagasse, and lignin content in gut sections, feces, and food bolus. The fiber's morphology was also evaluated. Bagasse breakdown occurs sequentially (foregut, midgut, hindgut) through mechanical grinding and glycosyl hydrolase activity. The foregut primarily reduces particle size (> 90%) through chewing and enzymatic action, aided by chitinous teeth. Sugarcane bagasse in the midgut resembled the foregut's morphology, while the hindgut and feces displayed microorganisms and small surface holes. The study also explored links between the distribution of monosaccharides and glycosyl hydrolase activity in gut chambers. Monosaccharide profiling revealed elevated levels of rhamnose (~ 1. 1.2 μg·mg⁻¹ CW) and galactose (~ 5 μg·mg⁻¹ CW) in the foregut/midgut, with xylose peaking in the foregut (~ 15 μg·mg⁻¹ CW). Fucose, mannose, arabinose, non-cellulosic, and cellulosic (~ 1, 4, 4.2, 6, 6.2, 7, and 48 μg· mg¹ CW, respectively) remained stable across gut regions. Lignin (20% of the cell wall) persisted undigested in bagasse and feces (~ 20% dry weight). Enzymatic profiling of digestive enzymes showed that the foregut and midgut exhibited higher soluble enzymatic activities against βGlc (~ 3), βXyl (~ 1. 8), αXyl (~ 0. 02), βGal (~ 1.6. 6), αGal (~ 1), βMan (~ 1.3. 3), αAra (~ 0. 0.8), βClb (~ 0. 8), βGlca (~ 0.3. 3), and αRha (~ 0. 006 μmol sugar min⁻¹ mg ptn⁻¹). The hindgut (the main microbial chamber) showed lower activity for most enzymes. Fecal analysis indicated digestion/absorption of ~ 50% cellulosic glucose, 25% non-cellulosic glucose, 21% arabinose, and 26% xylose. These findings suggest that P. americana is a promising hemicellulose/cellulose degradation model without lignin breakdown under mesophilic conditions.