基因工程菌株yarrowia lipolytica 30利用菊芋提取液产柠檬酸的分析-analysis of citric acid production from jerusalem artichoke extract by genetic engineering strain yarrow ia lipolytoica 30.docx

Studies on Citric acid production from extract of Jerusalem artichoke tubers by the genetically engineered yeast Yarrowia lipolytica strain 30AbstractAt present, citric acid (CA) is produced mainly by submerged fungal fermentation of sucrose or molasses or glucose medium using Aspergillus niger. However, the production of CA with the use A. niger is associated with the accumulation of significant amounts of solid and liquid wastes. In recent years, Yarrowia lipolytica has been considered as another potential producer of CA. However, for economical aspect, it becomes important to further improve CA production by Y. lipolytica via genetic engineering. In our previous study, the genetically engineered yeast Y. lipolytica 30 producing recombinant exo-inulinase in which ACL1 gene encoding ATP-citrate lyase was deleted and the copy number of the ICL1 gene encoding iso-citrate lyase was increased was obtained. During the 2-l fermentation, 84.0 g/l of citric acid in the fermented medium was attained from10.0 % of inulin by the genetically engineered yeast Y. lipolytica 30 within 214 h. In order to reduce the cost for citric acid production, extract of Jerusalem artichoke was used as the substrate for CA production by the genetically engineered yeast Y. lipolytica 30 in this study.“One-variable-at-a-time” method was used to optimize the conditions for extraction of sugar from Jerusalem artichoke tubers. The results showed that theoptimized extraction conditions were that the solid to liquid ratio was 1:20，theextraction time was 50 min，the extraction temperature was 100℃，the concentration of HCl was 0.05M，the extraction times was 4. Extract of Jerusalem artichoke tubers treated by Ca(OH)2 was used to produce CA by Y. lipolytica 30, 24.3 g L-1 citric acidwas produced and the yield of citric acid was 0.39 g g-1 within 12d. However, the yield of CA was 8.21g/l and the yield of citric acid was 0.17 g g-1 when the crude extract of Jerusalem artichoke was used.In this study