In natural produced bacteria, β-carotene hydroxylase (CrtZ) and β-carotene ketolase (CrtW) convert β-carotene into astaxanthin. To increase astaxanthin production in heterologous strain, simple and effective strategies based on the co-expression of CrtZ and CrtW were applied in E. coli. First, nine artificial operons containing crtZ and crtW genes from different sources were constructed and, respectively, introduced into E. coli ZF237T, a β-carotene producing host. Among the nine resulting strains, five accumulated detectable amounts of astaxanthin ranging from 0.49 to 8.07 mg/L. Subsequently, the protein fusion CrtZ to CrtW using optimized peptide linkers further increased the astaxanthin production. Strains expressing fusion proteins with CrtZ rather than CrtW attached to the N-terminus accumulated much more astaxanthin. The astaxanthin production of the best strain ZF237T/CrtZAs-(GS)1-WBs was 127.6% and 40.2% higher than that of strains ZF237T/crtZAsWBs and ZF237T/crtZBsWPs, respectively. The strategies depicted here also will be useful for the heterologous production of other natural products.

中文翻译：

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不同的β-胡萝卜素羟化酶和酮酶在大肠杆菌中的组合表达，以增加虾青素的产生。

在天然产生的细菌中，β-胡萝卜素羟化酶（CrtZ）和β-胡萝卜素酮醇酶（CrtW）将β-胡萝卜素转化为虾青素。为了增加异源菌株中虾青素的产量，在大肠杆菌中应用了基于CrtZ和CrtW共表达的简单有效策略。首先，构建了九个包含来自不同来源的crtZ和crtW基因的人工操纵子，并将其分别引入到生产β-胡萝卜素的宿主大肠杆菌ZF237T中。在这九个菌株中，五种累积检测到的虾青素含量在0.49至8.07 mg / L之间。随后，使用优化的肽接头将蛋白CrtZ与CrtW融合，进一步提高了虾青素的产量。表达带有CrtZ而不是附着于N端的CrtW的融合蛋白的菌株积累了更多的虾青素。最佳菌株ZF237T / CrtZAs-（GS）1-WBs的虾青素产量分别比菌株ZF237T / crtZAsWBs和ZF237T / crtZBsWPs高127.6％和40.2％。这里描述的策略对于其他天然产物的异源生产也将是有用的。