Effect of Alkaline and Mechanical Pretreatment of Wheat Straw on Enrichment Cultures from Pachnoda marginata Larva Gut

Abstract

In order to partially mimic the efficient lignocellulose pretreatment process performed naturally in the gut system of Pachnoda marginata larvae, two wheat straw pretreatments were evaluated: a mechanical pretreatment via cutting the straw into two different sizes and an alkaline pretreatment with calcium hydroxide. After pretreatment, gut enrichment cultures on wheat straw at alkaline pH were inoculated and kept at mesophilic conditions over 45 days. The methanogenic community was composed mainly of the Methanomicrobiaceae and Methanosarcinaceae families. The combined pretreatment, size reduction and alkaline pretreatment, was the best condition for methane production. The positive effect of the straw pretreatment was higher in the midgut cultures, increasing the methane production by 192%, while for hindgut cultures the methane production increased only by 149% when compared to non-pretreated straw. Scanning electron microscopy (SEM) showed that the alkaline pretreatment modified the surface of the wheat straw fibers, which promoted biofilm formation and microbial growth. The enrichment cultures derived from larva gut microbiome were able to degrade larger 1 mm alkaline treated and smaller 250 µm but non-pretreated straw at the same efficiency. The combination of mechanical and alkaline pretreatments resulted in increased, yet not superimposed, methane yield.

Biogenic Straw Aerogel Thermal Insulation Materials

“…[23][24][25] It can effectively disrupt the cell wall dissolving lignin and then produce cellulose-rich residues. [26,27] Moreover, during alkali pretreatment, OH À weakens the hydrogen bond between hemicellulose and cellulose and saponifies the ester bond between lignin and hemicellulose. [28] On the other hand, a dilute acid pretreatment modifies the microstructure and composition of fibers by partially hydrolyzing polysaccharides and reducing the crystallinity of cellulose.…”

The highly differentiated Pachnoda marginata gut hosts sequential microbiomes with biotechnological applications

“…Already before high throughput DNA sequencing was available, results from culturing techniques suggested substantial differences in the distribution of microbial taxa throughout the various sections of the intestinal tract of insects [12]. In the case of Pachnoda marginata, previous works have provided vague or partial descriptions on the composition of its gut microbiota mainly from enriched cultures on wheat straw [11,13] and sulfate containing media [14].…”