Date Published: July 3, 2018
Publisher: Public Library of Science
Author(s): Shuaijie Chai, Jianan Shi, Teng Huang, Yalu Guo, Jian Wei, Meicen Guo, Liyun Li, Shijuan Dou, Lijuan Liu, Guozhen Liu, Yiu Fai Tsang.
To reveal growth properties of Chlorella sorokiniana UTEX 1230, four monosaccharides (glucose, fructose, galactose and xylose) were individually supplemented into medium as carbon sources for the cultivation of C. sorokiniana UTEX 1230. Supplementation with glucose increased OD750, biomass and lipid yield but decreased protein abundance per unit dry weight of biomass under all concentrations examined, the maximum OD750, biomass and lipid yield increased 2.04, 6.78 and 12.43 times, respectively, compared with autotrophic controls. A low concentration of glucose (<4 g/L) simultaneously promoted the biosynthesis of chlorophylls and protein abundance per unit culture volume, but decreased the lipid content per unit dry weight of biomass and all supplemented glucose can be exhausted within 7 days. Higher glucose concentrations (≥4 g/L) decreased the biosynthesis of chlorophylls and protein abundance per unit culture volume, but increased the lipid content per unit dry weight of biomass. In glucose supplemented scenario, C. sorokiniana UTEX 1230 growth was light-independent. Supplementation with fructose promoted C. sorokiniana UTEX 1230 growth to a much lesser extent compared with glucose, whereas supplementation with galactose had no effect and supplementation with xylose even inhibited growth. Our findings represent basic experimental data on the effect of monosaccharides and can serve as the basis for a robust cultivation system to increase biomass and lipid yield.
Because large-scale use of fossil fuels has caused severe environmental pollution and is leading to their depletion, the development and use of renewable and sustainable energy sources is needed. In recent years, bioenergy has emerged as an attractive option because it can be produced from a variety of feedstocks, including vegetable oils, seed oils and other lipid-rich biomass materials [1–3]. Large-scale cultivation of oil crops is limited, however, by low oil yields and competition with agricultural land. Microalgae are theoretically more promising bioenergy resources offering significant advantages, such as fast growth , short growth cycles, high lipid yields , bioactive compounds production  and the ability to grow on non-crop lands and in salt water [7–11] or waste water . While primary technologies involving microalgae cultivation and lipid extraction have already been established , low yields and high bioenergy costs are key bottlenecks to industrial-scale exploitation of microalgae. Overcoming these challenges will require major efforts to optimize cultivation systems and further elucidate the mechanisms underlying lipid biosynthesis.
Four monosaccharides (glucose, fructose, galactose and xylose) were individually supplemented into medium as carbon sources for the cultivation of C. sorokiniana UTEX 1230. It was found that supplementation with glucose promoted the growth of C. sorokiniana UTEX 1230 dramatically. Supplementation with fructose promoted C. sorokiniana UTEX 1230 growth to a lesser extent compared with glucose, whereas supplementation with galactose had no effect and supplementation with xylose inhibited growth.