Converting corn wet‐milling effluent into high‐value fungal biomass in a biofilm reactor

Abstract

Rhizopus microsporus was grown in an attached growth system using corn wet-milling effluent as a growth medium. This strain was chosen due to its ability to effectively degrade organic matter in corn wet-milling effluent and for its properties to produce significant levels of protein, chitin and chitosan. Fungal growth and organic removal efficiency were examined under both aseptic and non-aseptic conditions with and without nutrient supplementation. Plastic composite support (PCS) tubes, composed of 50% (w/w) polypropylene (PP) and 50% (w/w) agricultural products were used as support media. Significantly higher organic removal measured as chemical oxygen demand (COD) and biomass yield were observed in the bioreactor with PCS tubes than in two control bioreactors; that is with PP tubes alone and suspended growth (without support media). This confirmed that the PCS support medium with agricultural components enhanced fungal growth and organic removal. The results showed that supplementation of nutrients (e.g., mineral salts) under aseptic conditions enhanced the COD removal from 50% to 55% and observed biomass yield from 0.11 to 0.16 g (dry-weight)/g COD(removed) (i.e., from 0.10 to 0.14 g volatile solids (VS)/g COD(removed) approximately). Non-aseptic operation without nutrient supplementation resulted in an observed biomass yield of 0.32 g volatile suspended solids (VSS)/g COD(removed) with no significant improvement in COD removal ( approximately 53%); whereas with nutrient supplementation, the observed biomass yield increased to 0.56 g VSS/g COD(removed) and COD removal improved to 85%. The fungal system was able to degrade the organic matter with concomitant production of high-value fungal biomass. This is the first study that examined the conversion of corn milling waste stream into high value fungal protein.

Innovative biorefinery concept for sugar-based ethanol industries: Production of protein-rich fungal biomass on vinasse as an aquaculture feed ingredient

“…With respect to the control, at the optimal vinasse concentration and pH, 51.72, 222.95, and 86.67% improvements in fungal biomass yield were derived from N and P supplemented rum-, molasses-, and cane-vinasse samples, respectively (Table 2). This finding closely agrees with the aseptic batch study of Jasti et al (2008) who reported 45.45% increase in fungal biomass yield in N and P supplemented corn wet-milling effluent compared to non-nutrient supplemented samples.…”

“…The maximal fungal biomass yields were 0.92 ± 0.04, 0.67 ± 0.05, and 0.61 ± 0.01 (g biomass increase/g initial biomass) for rum-, molasses-, and cane-vinasse, respectively. However, the optimal pH for fungal cultivation in corn-ethanol residue was reported to be 4.0 (Jasti et al, 2008;Rasmussen et al, 2007). This could be due to different chemical attributes of these substrates.…”

“…This finding indicated that the solid fraction of vinasse, which was attached to the biomass, did not significantly contribute to the amount of protein and lipid in fungal biomass itself. Furthermore, the fungus cultivated on rum-and molasses-vinasse was found to have higher protein content than that grown on thin stillage and corn wet-milling effluent, which contained about 43 and 37% protein, respectively (Jasti et al, 2008;Rasmussen et al, 2007).…”

Nutrient recovery from ethanol co-products by a novel mycoalgae biofilm: attached cultures of symbiotic fungi and algae

“…The adjustment of nutrient levels in the co‐products may have a positive influence on the nutrient removal efficiency. The supplementation of nutrients (mineral salts) enhanced the COD removal and observed biomass yield from 50% and 0.11 g (dry weight) g −1 COD removed to 55% and 0.16 g (dry‐weight) g −1 COD removed, respectively . The suspended solids removal (Fig.…”

Fungal Treatment of Crop Processing Wastewaters with Value-Added Co-Products

“…Under aseptic conditions in a nutrient medium, R. oligosporus was reported to produce a 3% yield of chitosan [71], as well as 4 and 40% yields of lysine and protein, respectively [72]. R. oligosporus was successfully cultivated on wheat milling and corn wet-milling streams, achieving significant reductions in COD of up to 80-90% [6,7,9,39,42,45,49,53,73,[74][75][76][77][78][79][80]. The filamentous nature of fungal mycelia and potential for pellet formation aid in the recovery of fungal biomass [9,14].…”