PRODUCTION OF LACTIC ACID FROM MIXED FEED OF PAPER MILL SLUDGE AND HEMP HURD BY SIMULTANEOUS SACCHARIFICATION AND CO-FERMENTATION

A mixture of paper mill sludge and hemp hurd was investigated as a raw material for lactic acid (LA) production by way of simultaneous saccharification and co-fermentation (SSCF). The SSCF was carried out using the Cellic C-Tec2 enzyme and Lactobacillus pentosus (ATCC-8041) without pH control, using the ash content existing in the sludge (primarily calcium carbonate) as a neutralizing reagent. From SSCF experiments with various ratios of the two solid feedstocks, it was found that a minimum sludge-to-hemp hurd ratio of 3: 1 is required to maintain the pH near optimum and provide high LA yield. From multiple SSCF runs, LA concentrations of 52-67 g/L and LA yields of 0.69-0.82 g/g sugars were achieved from mixed feed under conditions of 10%-12% solids loading and 15 FPU/g-glucan enzyme loading.