| Xylose as xylitol raw material and functional food additive, its market demand is bigger and bigger. The raw material of xylose production is mainly from corn cob and crop straw. Due to the hydrolyzate contains a variety of organic acids and sugars, the xylose purification process is relatively complicated. How to purify xylose simply and rapidly is the key technology of xylose preparation. In this research, a Pichia mutant for xylose metabolic defect was constructed in order to use the nutrients in hydrolyzed corn cobs with microbial, and to purify xylose and enrich the valued by-products simutaneously.Main conclusions are as follows:1-. The condition for P. pastoris spore induction was studied. The results showed that the optimal condition is 10 g/L sodium acetate,6 g/L potassium chloride,10 g/L glucose and 1 mL/L of trace element,20 g/L agar when cultivated at 28? for 7 days. The spore production rate can reach 72%.2%The haploids Pichia were obtained when treating the living spore in 3%snaillase at 30? for 2 hours followed by 58? water bath for 12 minutes.3%The xylose reductase gene, xyl gene, was knocked out by homologous recombination. The mutants has no ability for xylose metabolism.4?The factors, time, temperature, concentration of sulfuric acid and other factors, influencing corncob hydrolyzing were studied. The results showed that the optimum conditions of acid hydrolysis corncob as follows:0.5% sulfuric acid hydrolysis under 85 ? for 48 hours. The reducing sugar yield about was 30%.5?The Pichia HM mutants for xylose metabolism defect when cultivated at corncobs hydrolysis solution without other nutrient components addition, can grow well. Compared with the wild type, the mutant cannot use the reductive sugar when glucose used up in the corncobs hydrolysis solution. |
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