Production of spent mushroom substrate hydrolysates useful for cultivation of Lactococcus lactis by dilute sulfuric acid, cellulase and xylanase treatment

Spent mushroom substrate (SMS) was treated with dilute sulfuric acid followed by cellulase and xylanase treatment to produce hydrolysates that could be used as the basis for media for the production of value added products. A L9 (34) orthogonal experiment was performed to optimize the acid treatment process. Pretreatment with 6% (w/w) dilute sulfuric acid at 120 °C for 120 min provided the highest reducing sugar yield of 267.57 g/kg SMS. No furfural was detected in the hydrolysates. Exposure to 20 PFU of cellulase and 200 XU of xylanase per gram of pretreated SMS at 40 °C resulted in the release of 79.85 g/kg or reducing sugars per kg acid pretreated SMS. The dilute sulfuric acid could be recycled to process fresh SMS four times. SMS hydrolysates neutralized with ammonium hydroxide, sodium hydroxide, or calcium hydroxide could be used as the carbon source for cultivation of Lactococcus lactis subsp. lactis W28 and a cell density of 2.9 × 1011 CFU/mL could be obtained. The results provide a foundation for the development of value-added products based on SMS.