Department of Biotechnology and Food Microbiology, Wroclaw University of Environmental and Life Sciences, 37 Chełmońskiego St, 51-630, Wroclaw, Poland.
BMC Biotechnol. 2019 Feb 11;19(1):11. doi: 10.1186/s12896-019-0503-0.
Citric acid is considered as the most economically feasible product of microbiological production, therefore studies on cheap and renewable raw materials for its production are highly desirable. In this study citric acid was synthesized by genetically engineered strains of Yarrowia lipolytica from widely available, renewable polysaccharide - inulin. Hydrolysis of inulin by the Y. lipolytica strains was established by expressing the inulinase gene (INU1 gene; GenBank: X57202.1) with its native secretion signal sequence was amplified from genomic DNA from Kluyveromyces marxianus CBS6432. To ensure the maximum citric acid titer, the optimal cultivation strategy-repeated-batch culture was applied.
The strain Y. lipolytica AWG7 INU 8 secreted more than 200 g dm of citric acid during repeated-batch culture on inulin, with a productivity of 0.51 g dm h and a yield of 0.85 g g.
The citric acid titer obtained in the proposed process is the highest value reported in the literature for Yarrowia yeast. The obtained results suggest that citric acid production from inulin by engineered Y. lipolytica may be a very promising technology for industrial citric acid production.
柠檬酸被认为是微生物生产中最具经济可行性的产品，因此，人们非常希望研究其生产用廉价且可再生的原料。在这项研究中，通过基因工程化的解脂耶氏酵母（Yarrowia lipolytica）菌株，从广泛可用的可再生多糖菊粉（inulin）中合成了柠檬酸。通过表达来自马克斯克鲁维酵母（Kluyveromyces marxianus CBS6432）的基因组 DNA 中的菊粉酶基因（INU1 基因；GenBank：X57202.1）及其天然分泌信号序列，使 Y. lipolytica 菌株水解菊粉。为了确保获得最大的柠檬酸产量，采用了最佳的培养策略——重复分批培养。
在菊粉上进行重复分批培养时，AWG7 INU8 型解脂耶氏酵母菌株可分泌超过 200 g/dm 的柠檬酸，其生产力为 0.51 g/dm/h，产率为 0.85 g/g。
所提出的工艺中获得的柠檬酸产量是文献中报道的解脂耶氏酵母的最高值。研究结果表明，通过工程化的解脂耶氏酵母从菊粉生产柠檬酸可能是工业柠檬酸生产的一项很有前途的技术。
