A biotech-systematic approach to select fungi for bioconversion of winery biomass wastes to nutrient-rich feed

Abstract

Grape marc and lees are main waste biomass in wine industry, which contain substantial amount of carbohydrates and nutrients, but currently deliver considerable carbon emission through landfill in Australia. This study was aimed to develop a biotechnological systematic approach to select suitable fungi for bioconversion of the winery biomass wastes into animal feed. The biotech-systematic approach was developed through assessment of nutrient/carbon source accessibility of the fungi, understanding of their metabolic reactions in solid state fermentation, and nutritive value of the fungi-fermented grape marc. From 13 Aspergillus, Rhizopus, and Trichoderma fungal species, A. oryzae DAR 3699, A. oryzae RIB40 and T. reesei RUT C30 were determined as the best fungi due to their promising biochemical capabilities to enhance protein contents and in vitro digestibility of grape marc in mono- and co-cultivations. The mono-fungous-cultured SSF process used these selected fungi is able to convert grape marc to nutrient-rich feed by increasing the protein contents from ∼5% to 26% and the digestibility from ∼25% to over 50%. R. oligosporus 2710 with R. oryzae 6201 or T. viride 15719 showed promising protein enrichment to 18–23% and digestibility improvement by ∼50% in their co-cultivations. This preliminary bioengineering strategy will be useful for selecting microorganisms for the bioconversion of organic wastes to high valuable products. This “green cycle” bioprocess will be useful to promote the old-fashioned waste treatment technologies for the cleaner production in food processing industries.