Recovery of glucose from dried distiller's grain with solubles using combinations of solid-state fermentation and insect culture

A bioethanol byproduct (dried distillerâ s grains with solubles; DDGS) contains a high cellulose and starch. We hypothesized combinations of solid-state fermentation (SSF) and digestion by black soldier fly larvae (BSFL) (Hermetia illucens) could increase the recovery of glucose from this byproduct through concentrating and loosening cellulose matrix by their activities. DDGS was individually fermented with Aspergillus niger, Aspergillus fumigatus, Trichoderma koningii, Phanerochaete chrysosporium, or Lactobacillus plantarum. The fermented DDGS was fed to BSFL, and glucose recoveries from spent feeds were conducted. SSF increases lipid and protein contents, supporting BSFL growth, as well as weakening cellulosic matrix. BSFL use nutrients in SSF-DDGS, further concentrating and weakening cellulose, i.e., DDGS becomes a half without changing cellulose contents. For example, Lactobacillus plantarum SSF with BSFL culture concentrates the cellulose content from 9.7% to 26.5% of spent feed. Glucose recovery was determined using three sequential processes (free glucose determination, weak-acid hydrolysis of amorphous cellulose and enzymatic hydrolysis of micronized crystalline cellulose). Total glucose obtained from 100g of DDGS increases from 4.8 g to 10.7g. These results show that the combinations of SSF and BSFL would provide additional fermentable sugars (and insect biomass) from bioethanol byproducts, suggesting a high productivity from the same feedstock.

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