Abeln, F, Henk, D, Moreno, M, Hicks, R, Auta, H & Longanesi, L 2020,

Abstract

AbstractBackgroundHeterotrophic 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 pulcherrimais 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. pulcherrimawas 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 ofM. pulcherrima, enzyme-hydrolysed starch in the form of glucose syrup was selected as fermentation feedstock.ResultsIn batch fermentations on the 2-L scale, a lipid concentration of 14.6 g L−1and productivity of 0.11 g L−1 h−1were 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−1consumed 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.ConclusionsThe results establish the importance ofM. pulcherrimafor industrial biotechnology and its suitability to commercially produce a food-grade oil. Further improvements in the productivity are required to makeM. pulcherrimalipid production industrial reality, particularly when longer-chain saccharides are involved.