Heterotrophic microbial oils are potentially a more sustainable alternative to vegetable or fossil oils for food and fuel applications. However, as almost all work in the area is conducted on the laboratory scale, such studies carry limited industrial relevance and do not give a clear indication of what is required to produce an actual industrial process. Metschnikowia pulcherrima is a non-pathogenic industrially promising oleaginous yeast which exhibits numerous advantages for cost-effective lipid production, including a wide substrate uptake, antimicrobial activity and fermentation inhibitor tolerance. In this study, M. pulcherrima was fermented in stirred tank reactors of up to 350 L with 250-L working volume in both batch and semi-continuous operation to highlight the potential industrial relevance. Due to being food-grade, suitable for handling at scale and to demonstrate the oligosaccharide uptake capacity of M. pulcherrima, enzyme-hydrolysed starch in the form of glucose syrup was selected as fermentation feedstock. In batch fermentations on the 2-L scale, a lipid concentration of 14.6 g L−1 and productivity of 0.11 g L−1 h−1 were achieved, which was confirmed at 50 L (15.8 g L−1; 0.10 g L−1 h−1). The maximum lipid production rate was 0.33 g L−1 h−1 (daily average), but the substrate uptake rate decreased with oligosaccharide chain length. To produce 1 kg of dry yeast biomass containing up to 43% (w/w) lipids, 5.2 kg of the glucose syrup was required, with a lipid yield of up to 0.21 g g−1 consumed saccharides. In semi-continuous operation, for the first time, an oleaginous yeast was cultured for over 2 months with a relatively stable lipid production rate (around 0.08 g L−1 h−1) and fatty acid profile (degree of fatty acid saturation around 27.6% w/w), and without contamination. On the 250-L scale, comparable results were observed, culminating in the generation of nearly 10 kg lipids with a lipid productivity of 0.10 g L−1 h−1. The results establish the importance of M. pulcherrima for industrial biotechnology and its suitability to commercially produce a food-grade oil. Further improvements in the productivity are required to make M. pulcherrima lipid production industrial reality, particularly when longer-chain saccharides are involved.

中文翻译：

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在淀粉水解物上使用 Metschnikowia pulcherrima 进行半连续中试规模微生物油生产。

异养微生物油可能是用于食品和燃料应用的植物油或化石油的更可持续替代品。然而，由于该领域的几乎所有工作都是在实验室规模上进行的，因此此类研究的工业相关性有限，并且没有明确表明生产实际工业过程所需的条件。Metschnikowia pulcherrima 是一种非致病性的工业化产油酵母，具有成本效益高的脂质生产优势，包括广泛的底物吸收、抗菌活性和发酵抑制剂耐受性。在这项研究中，M. pulcherrima 在高达 350 L 和 250 L 工作体积的搅拌罐反应器中以间歇和半连续操作方式发酵，以突出潜在的工业相关性。由于是食品级，适合于规模化处理并证明 M. pulcherrima 的寡糖吸收能力，选择葡萄糖浆形式的酶水解淀粉作为发酵原料。在 2-L 规模的分批发酵中，脂质浓度为 14.6 g L-1，产量为 0.11 g L-1 h-1，这在 50 L（15.8 g L-1；0.10 g L- 1 h-1)。最大脂质产生率为 0.33 g L-1 h-1（日平均值），但底物摄取率随着寡糖链长度的增加而降低。为了生产 1 kg 含有高达 43% (w/w) 脂质的干酵母生物质，需要 5.2 kg 葡萄糖浆，脂质产量高达 0.21 g g-1 消耗的糖类。在半连续运行中，第一次，一种含油酵母培养了两个多月，具有相对稳定的脂质生产率（约 0.08 g L-1 h-1）和脂肪酸分布（脂肪酸饱和度约为 27.6% w/w），并且没有污染。在 250-L 规模上，观察到了类似的结果，最终产生了近 10 kg 的脂质，脂质生产力为 0.10 g L-1 h-1。结果确定了 M. pulcherrima 对于工业生物技术的重要性及其在商业生产食品级油方面的适用性。需要进一步提高生产力以使 M. pulcherrima 脂质生产成为工业现实，特别是在涉及长链糖类时。观察到了类似的结果，最终产生了近 10 kg 的脂质，脂质生产力为 0.10 g L-1 h-1。结果确定了 M. pulcherrima 对于工业生物技术的重要性及其在商业生产食品级油方面的适用性。需要进一步提高生产力以使 M. pulcherrima 脂质生产成为工业现实，特别是在涉及长链糖类时。观察到了类似的结果，最终产生了近 10 kg 的脂质，脂质生产力为 0.10 g L-1 h-1。结果确定了 M. pulcherrima 对于工业生物技术的重要性及其在商业生产食品级油方面的适用性。需要进一步提高生产力以使 M. pulcherrima 脂质生产成为工业现实，特别是在涉及长链糖类时。