The Preparation Of Corn Cob Hydrolysate And The Optimization Of Yeast Protein Fermentation

The main content of my paper is the preparation of corn cob hydrolysate and the fermentation of Candida intermedia strain3. The results are as follows:(1) Through orthogonal experiment design, we optimized the diluted sulphuric acid hydrolysis process and found out the optimum conditions: sulphuric acid concentration3%, material/acid=1:12, hydrolysis temperature121℃, hydrolysis time90min. In these conditions, the yield of reducing sugar to corn cob dry weight was35.87%. The reducing sugar concentration in hydrolysate was33.37g/L, and TN=1.08g/L, C:N≈13:1. With the similar method, we found out the optimum condition of concentrated sulphuric acid hydrolysis process were: material/acid=1:5, sulfuric acid pretreatment concentration60%, pretreatment time3h, sulfuric acid hydrolysis concentration3%, hydrolysis temperature105℃, hydrolysis time60min. In these conditions, the yield of reducing sugar to corn cob dry weight was60.44%. Reducing sugar concentration was6.44g/L, TN was0.11g/L,the C:N=23.5:1.(2) With HPLC analysis, we can found that in the diluted sulphuric acid hydrolysate, xylose concentration was23.4184g/L, and glucose concentration was11.8046g/L. Xylose and glucose quality ratio was about1.98:1. In the concentrated sulphuric acid hydrolysate xylose concentration was2.5203g/L, and glucose concentration was4.1365g/L. Xylose and glucose quality ratio was about0.61:1. After a comprehensive study, we took the diluted sulphuric acid hydrolysis process as what we use in lab.(3) The culture medium which was used to ferment the corn cob hydrolysate was optimized. Making use of the fractional factorial design we found that the best nitrogen source for strain3was urea; after the single factor experiment we found the best inorganic salt for str.3was potassium dihydrogen phosphate. The nine factors of twelve times Plackett-Burman experiment was used and five growth factors (biotin, inositol, amino acid, pyridoxine, and lactoflavin) were find which could improve the conversion significantly. After optimization, the culture medium formula was urea (the C:N=4:1 was controlled when urea was added), potassium dihydrogen phosphate2g/L, biotin2mg/L, inositol20mg/L, amino acid2mg/L, hydrochloric acid pyridoxine2mg/L, lactoflavin4mg/L. In these conditions, the cell dry weight in medium was1.51%, and the conversion rate reached up to45.02%.(4) The continuous feed-batch fermentation could improve the cell dry weight significantly. The result of the fermentation in10L fermenter showed that when the total sugar content was8.6%, just after40h fermentation, the cell dry weight go up to3.46%, and the conversion was40.1368%.