Acid Hydrolysis of Brewers’ Industrial Wastes and Their Use for Lipid Production by Oleaginous Yeasts

摘要

Brewers’ spent grain (BSG) and spent yeast cell (SYC) are the wastes from mashing and fermentation process of beer. The compositions of BSG were 24.49 ± 0.91% hemicellulose, 20.86 ± 0.60% cellulose and 9.62 ± 0.40% lignin, while those of SYC were 46.97 ± 0.07% protein, 21.32 ± 0.08% carbohydrate and 5.73 ± 0.57% lipids. BSG and SYC were acid hydrolyzed using different solid loadings at 5–24%. The optimal solid loadings for BSG and SYC that gave maximum sugar concentration were 15% and 24%, respectively. Sugar compositions in BSG hydrolysate were 22.02 ± 0.8% glucose, 45.83 ± 1.53% xylose, and 32.13 ± 2.3% arabinose, while those found in SYC hydrolysate were 31.43 ± 0.38% glucose and 69.57 ± 1.04% mannose. Both hydrolysates were used as nutrient sources at the same sugar concentration of 40?g/L for cultivation of three oleaginous yeasts, Trichosporonoides spathulata JU4-57, Rhodotorula mucilaginosa G43 and Yarrowia lipolytica TISTR 5151. BSG hydrolysate gave higher biomass than SYC hydrolysate possibly due to a higher content of suitable sugars for cell growth. Among three yeasts, T. spathulate JU4-57 gave the highest lipid yields of 62.9 ± 5.67 and 39.9 ± 0.62?mg/g-substrate on BSG and SYC hydrolysates, respectively. This study may contribute greatly to low-cost production of oil sources for biodiesel production and may help to increase the environmental and economic sustainability of the brewery business.