Manufacture of bran qu with Monascus and optimization of the conditions of esterifying Huang shui

In the present study,the bran qu was manufactured with Monascus by a salver fermentation method,the objective of this study was to provide a solid- state fermentation method which consumed less time and prevented bacterial contamination.A single factor experiment was conducted to investigate the effect of the ratio of materials,material thickness,moisture content,cultivation temperature and time on the esterifying capacity of bran qu. The optimal manufacture conditions of bran qu were determined based on the esterifying capacity.In addition,the bran qu was applied to esterify Huang shui to improve the ethyl capronate and ethyl lactate contents.Also the effect of initial ethanol content and p H on the esterifying process was studied by comparing the relative contents of total esters and volatile compounds detected by GC- MS,the esterifying conditions of Huang shui were optimized in order to reuse the liquor byproducts.The results showed that the optimal fermentation conditions of bran qu were as follows: ratio of raw materials( bran ∶ yellow water ∶ tap water,100 ∶ 15 ∶ 75,w / v / v),material thickness( 1.8 cm),moisture( 47%),cultivation temperature( 32 ℃) and time( 48 h). The results of esterifying Huang shui suggested that when the initial ethanol contents were 15% and 20% respectively,initial p H was 3.5,and enzymatic reaction time was 15 d,the content of total esters obtained were 0.63 g /100 m L and 0.64 g /100 m L respectively,among which the relative contents of representative components( ethyl capronate and ethyl lactate) were respectively increased from 14.33% to 42.70% and 31.30%.