Bioprocess development with special yeasts for cassava bagasse enrichment nutritional to use in animal feed

Abstract

In general, the low-protein agro-industrial residues like cassava bagasse are cheaper but limited in feed use. However, if through an economically attractive bioprocess, these residues are transformed into nutritionally enriched products, the animal protein manufacturing cost afford to be diminished. This work aimed to establish an original biological treatment based on special yeasts for cassava bagasse enriching. Batch and Fed-Batch cultures, with raw (CB) or hydrolyzed cassava bagasse (HCB) and corn steep liquor (CSL), were used to screen promising yeasts for valorizing cassava residue. Among the four assessed yeasts (Rhodotorula sp. LABI1, Wickerhamomyces onychis LABI2, Sporidiobolus pararoseus Sia 33.1, Sporobolomyces japonicus Sia 70a), the cultures of S. japonicus Sia 70a produced more biomass when the culture medium comprised 0.5 % CSL and 5.0 % CB (8.6 g/L yeast biomass, biomass-substrate yield factor; [Formula presented], and maximum specific growth rate; µmax=0.03h−1). However, S. pararoseus Sia 33.1 (11.6 %), W. onychis LABI2 (8–15 %) and S. japonicus Sia 70a (11.8 %) were responsible for higher protein content in the CB due to the yeast biomass incorporated at the end of the process. Amylases were also detected in some cultures (up to 0.4 U/mL), which could improve the cassava bagasse digestibility. These results showed bioprocessing potential by these special yeasts to convert the low-protein cassava bagasse into a nutritionally enriched product. Now a biological evaluation with animals is needed to approve this method for feed purposes.