目的 通过添加芳香族氨基酸促进井冈霉素生物合成起始单位的供应,提高其发酵产量.方法 优化苯丙氨酸添加时间和浓度确定最优添加条件,分析前体代谢相关的酶活考察其影响机制.结果 确定苯丙氨酸最佳添加条件为在发酵第24h添加0.1g/L.发现37℃时苯丙氨酸的添加提高了井冈霉素A产量,但在42℃条件下提高幅度大大降低.通过分析6-磷酸葡萄糖脱氢酶酶活,发现芳香族氨基酸添加并未影响其酶活.结论 苯丙氨酸的添加能有效提高井冈霉素发酵产量近60％.苯丙氨酸的添加可能通过反馈抑制降低了戊糖磷酸途径中中间体的消耗,从而为井冈霉素合成提供了更加充足的7-磷酸景天庚酮糖.%Objective To enhance validamycin production, aromatic amino acid was added to the medium to increase the supply of precursor for validamycin. Methods Phenylalanine, tryptophan and tyrosine were added to the medium to study the effect of aromatic amino acids on validamycin production. Addition time and concentration of phenylalanine were optimized to find out the optimal condition. The glucose-6-phosphate dehydrogenase (G6PDH) activity which related to validanycin precursor metabolism was analyzed to study its mechanism. Results The results showed that phenylalanine had the best effect on validamycin production. The optimal condition was 0.1 g/L phenylalanine added at 24h, which enhanced validamycin production by 60%. The addition of phenylalanine enhanced validamycin production greatly at 37℃, but not so much at 42 ℃. G6PDH activity was higher at 42 ℃ than 37℃, and it was found that the addition of phenylalanine had no significant effect on glucose-6-phosphate dehydrogenase activity. Conclusion Validamycin production was enhanced 60% by addition of phenylalanine. The addition of phenylalanine might inhibited the consumption of intermediates in pentose phosphate pathway, which resaved precursor for validamycin production. Precursors of many antibiotics come from pentose phosphate pathway, so this work also have reference value for enhancing other antibiotics production.
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