L-色氨酸重组高产菌株发酵工艺的优化

Optimization of fermentation process for recombinant high yield strain of L-tryptophan

L-色氨酸(L-tryptophan,L-Trp)是一种限制性氨基酸,是人体和动物体生长发育等重要生理活动的必需氨基酸之一,也是合成许多活性物质的关键氨基酸之一,广泛应用于医药、饲料和食品等方面,具有十分重要的商业价值。微生物发酵生产的L-色氨酸近些年来一直备受关注,主要是因为其价格低廉、纯度高、易分离等特点,因此利用微生物生产L-色氨酸在大规模工业生产上具有十分可观的应用前景。利用色氨酸高产基因,经基因工程重组到大肠杆菌内,筛选出色氨酸高产菌株。通过控制溶氧、碳源、p H值及残糖含量来有效提高L-色氨酸的产量。利用原始菌株探究发酵过程中发酵罐内的残糖含量,发现残糖含量控制在1%时,菌体生长最为良好,生长周期最长。将不同比例的糖蜜与葡萄糖混合,作为发酵时的碳源,结果显示当比例为3∶1时L-色氨酸产量最大;在发酵过程中控制p H条件,将产量提高到18.9 g/L;将溶氧条件控制在35%、40%两个范围,结果显示溶氧40%时L-色氨酸的产量达到27 g/L;将补料碳源换为60%的葡萄糖及70%的小麦糖,结果显示葡萄糖作为唯一碳源时,L-色氨酸产量较高。

L-tryptophanine （L-Trp） is a kind of restricted amino acid, which is one of the essential amino acids for the growth anddevelopment of human body and animal. It is one of the key amino acids in the synthesis of many active substances and has beenwidely used in medicine. The production of L- tryptophan by microbial fermentation has attracted much attention in recent years,mainly because of its low price, high purity and easy separation. Therefore, the production of L-tryptophan by microorganism hasa promising application prospect in large-scale industrial production. In this paper, the tryptophan high yield gene wasrecombined into Escherichia coli by genetic engineering. By controlling dissolved oxygen, pH value of carbon source andresidual sugar content, the yield of L-tryptophan was effectively increased by direct fermentation. In this experiment, the originalstrain was used to explore the content of residual sugar in fermenting tank. It was found that when the residual sugar content wascontrolled at 1%, the growth of bacteria was the best and the growth cycle was the longest. When molasses were mixed withglucose as carbon source during fermentation, the results showed that the yield of L-tryptophan was the highest when the ratiowas 3∶1; then when the pH was controlled during fermentation, the yield was increased to 18.9 g/L;the dissolved oxygencondition was controlled in the range of 35% and 40%. The results showed that the production of L-tryptophan reached 27 g/L atdissolved oxygen 40%; Finally, 60% glucose and 70% wheat sugar were replaced by carbon source. The results showed that theyield of L-tryptophan was higher when glucose was the sole carbon source.