Anthocyanins are widely distributed pigments in flowering plants with red, purple or blue colours. Their properties in promoting heath make anthocyanins perfect natural colourants for food additives. However, anthocyanins with strong colour and stability at neutral pH, suitable as food colourants are relatively rare in nature. Acylation increases anthocyanin stability and confers bluer colour. In this study, we isolated two anthocyanin regulators SbMyb75 and SbDel from S. baicalensis, and showed that constitutive expression of the two TFs led to accumulation of anthocyanins at high levels in black carrot hairy roots. However, these hairy roots had severe growth problems. We then developed a β-estradiol inducible system using XVE and a Lex-35S promoter, to initiate expression of the anthocyanin regulators and induced this system in hairy roots of black carrot, tobacco and morning glory. Anthocyanins with various decorations were produced in these hairy roots without any accompanying side-effects on growth. We further produced highly acylated anthocyanins with blue colour in a 5 L liquid culture in a bioreactor of hairy roots from morning glory. We provide here a strategy to produce highly decorated anthocyanins without the need for additional engineering of any of the genes encoding decorating enzymes. This strategy could be transferred to other species, with considerable potential for natural colourant production for the food industries.

花青素是开花植物中广泛分布的色素，呈红色、紫色或蓝色。花青素具有促进健康的特性，使其成为食品添加剂的完美天然着色剂。然而，适合作为食品着色剂的具有强烈颜色和在中性pH下稳定的花青素在自然界中相对较少。酰化增加了花青素的稳定性并赋予更蓝色的颜色。在本研究中，我们从S中分离出两种花青素调节剂SbMyb75和SbDel。黄芩，并表明这两个转录因子的组成型表达导致黑胡萝卜毛状根中花青素的高水平积累。然而，这些毛状根存在严重的生长问题。然后，我们使用 XVE 和 Lex-35S 启动子开发了 β-雌二醇诱导系统，以启动花青素调节剂的表达，并在黑胡萝卜、烟草和牵牛花的毛状根中诱导该系统。这些毛状根中产生了具有各种装饰的花青素，并且对生长没有任何副作用。我们进一步在牵牛花毛状根生物反应器中的 5 L 液体培养物中生产了高度酰化的蓝色花青素。我们在此提供了一种生产高度装饰花青素的策略，而不需要对任何编码装饰酶的基因进行额外的工程改造。这一策略可以转移到其他物种，在食品工业天然着色剂生产方面具有巨大的潜力。