Due to their capability of photosynthesis and autotrophic growth, cyanobacteria are currently investigated with regard to the sustainable production of a wide variety of chemicals. So far, however, no attempt has been undertaken to engineer cyanobacteria for the biotechnological production of vitamins, which is probably due to the light-sensitivity of many of these compounds. We now describe a photoautotrophic bioprocess to synthesize riboflavin, a vitamin used as a supplement in the feed and food industry. By overexpressing the riboflavin biosynthesis genes ribDGEABHT from Bacillus subtilis in the marine cyanobacterium Synechococcus sp. PCC 7002 riboflavin levels in the supernatant of the corresponding recombinant strain increased 56-fold compared to the wild-type. Introduction of a second promoter region upstream of the heterologous ribAB gene – coding for rate-limiting enzymatic functions in the riboflavin biosynthesis pathway – led to a further increase of riboflavin levels (211-fold compared to the wild-type). Degradation of the light-sensitive product riboflavin was prevented by culturing the genetically engineered Synechococcus sp. PCC 7002 strains in the presence of dichromatic light generated by red light-emitting diodes (λ = 630 and 700 nm). Synechococcus sp. PCC 7002 naturally is resistant to the toxic riboflavin analog roseoflavin. Expression of the flavin transporter pnuX from Corynebacterium glutamicum in Synechococcus sp. PCC 7002 resulted in roseoflavin-sensitive recombinant strains which in turn could be employed to select roseoflavin-resistant, riboflavin-overproducing strains as a chassis for further improvement.

由于它们的光合作用和自养生长能力，蓝藻目前正在研究各种化学品的可持续生产。然而，到目前为止，还没有尝试设计蓝藻以生物技术生产维生素，这可能是由于这些化合物中的许多对光敏感。我们现在描述合成核黄素的光自养生物过程，核黄素是一种在饲料和食品工业中用作补充剂的维生素。通过过表达核黄素生物合成基因ribDGEABHT从枯草芽孢杆菌在海洋蓝藻聚球藻sp. 与野生型相比，相应重组菌株上清液中的 PCC 7002 核黄素水平增加了 56 倍。在异源ribAB基因上游引入第二个启动子区域- 编码核黄素生物合成途径中的限速酶功能 - 导致核黄素水平进一步增加（与野生型相比增加了 211 倍）。通过培养基因工程聚球藻，防止了光敏产品核黄素的降解。PCC 7002 在红色发光二极管 (λ = 630 和 700 nm) 产生的二色光存在时发生应变。聚球藻属 PCC 7002 天然对有毒的核黄素类似物玫瑰黄素具有抗性。黄素转运蛋白的表达pnuX从谷氨酸棒状杆菌在聚球藻。PCC 7002 产生了玫瑰黄素敏感的重组菌株，这些菌株反过来可用于选择玫瑰黄素抗性、核黄素过度产生的菌株作为进一步改进的框架。