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Backset valorization in dry-grind ethanol process by co-culture of edible filamentous fungi and fodder yeast

Witold Pietrzak, Joanna Kawa-Rygielska
Journal of cleaner production 2019 v.220 pp. 376-385
Aspergillus oryzae, Candida utilis, Rhizopus microsporus var. oligosporus, amylases, biomass, coculture, corn, essential amino acids, ethanol, forage, fungal growth, glycerol, lactic acid, lipid content, lipids, liquids, mash, yeasts
In this study, edible filamentous fungi Aspergillus oryzae and Rhizopus oligosporus were co-cultured with fodder yeast Candida utilis using corn thin stillage to produce feed-grade biomass, amylases, and ethanol with the purpose of backset valorization. The co-culture of A. oryzae with C. utilis inoculated after 24 h of pure fungal growth provided the most promising results, yielding 18.6 g L−1 biomass with 41 and 31% of lipid and protein, respectively, with all of the essential amino acids. The microorganisms consumed nearly 34% of the cultivation medium solids, as well as 33% of glycerol and 12% of lactic acid, which allowed them to produce ca. 4.5 g L−1 ethanol and 1.7 U mL−1 amylase. The liquid fraction of the cultivation medium was used as 200 mL L−1 backset for the production of high-solids corn mash. The final ethanol concentrations reached 78.3, 90.6 and 108.2 g L−1 in the control sample (without backset), unfermented backset addition and fermented backset addition, respectively. This suggests that the yeast-fungi co-culture for backset treatment was effective in improving the core production stage in an ethanol-producing plant.