Method for efficiently producing lactic acid by fermenting brewers' spent grains

A method for efficiently producing lactic acid by fermenting brewers' spent grains, comprising the following steps:

• adding a NaOH alkali solution with a concentration of 1.0 wt % into brewers' spent grains according to a solid-liquid weight ratio of 1:10, cooking at 120° C. for 15 min, carrying out a solid-liquid separation, obtaining and washing solid residues to a neutral state, and obtaining alkali-pretreated brewers' spent grains;
• adding water to 20 g of the alkali-pretreated brewers' spent grains so as to adjust a solid content of a fermentation production system to 10%, adding cellulase into the alkali-pretreated brewers' spent grains according to an addition amount of 5 FPU/g, carrying out hydrolysis at 50° C. and pH of 5.0 for 20 hours, and obtaining a prehydrolyzed substrate;
• inoculating the prehydrolyzed substrate with a lactic acid bacteria seed solution with a viable count of 3.7×108 CFU/mL according to an inoculation amount at a volume ratio of 10%, fermenting at 43° C. and pH of 6.0 for 96 hours, and obtaining a fermentation broth containing the lactic acid;
• and
• wherein a dry basis of the alkali-pretreated brewers' spent grains contains 18.2% of cellulose and 20.4% of hemicellulose;
• and
• wherein a lactic acid concentration of the fermentation broth is not smaller than 50 g/L.

A method for efficiently producing lactic acid by fermenting brewers' spent grains, comprising the following steps:

• adding a NaOH alkali solution with a concentration of 1.0 wt % into brewers' spent grains according to a solid-liquid weight ratio of 1:10, cooking at 120° C. for 15 min, carrying out a solid-liquid separation, obtaining and washing solid residues to a neutral state, and obtaining alkali-pretreated brewers' spent grains;
• adding water to 20 g of the alkali-pretreated brewers' spent grains so as to adjust a solid content of a fermentation production system to 10%, adding cellulase into the alkali-pretreated brewers' spent grains according to an addition amount of 7.5 FPU/g, carrying out hydrolysis at 50° C. and pH of 5.0 for 30 hours, and obtaining a prehydrolyzed substrate;
• inoculating the prehydrolyzed substrate with a lactic acid bacteria seed solution with a viable count of 3.7×108 CFU/mL according to an inoculation amount at a volume ratio of 10%, fermenting at 43° C. and pH of 6.0 for 84 hours, and obtaining a fermentation broth containing the lactic acid;
• and
• wherein a dry basis of the alkali-pretreated brewers' spent grains contains 18.2% of cellulose and 20.4% of hemicellulose;
• and
• wherein a lactic acid concentration of the fermentation broth is not smaller than 45 g/L.