Heterotrophic or mixotrophic culture of microalgae is feasible alternative approach to avoid light limitation in autotrophic culture. However, only a few kinds of organic carbon sources are available for algal culture. Disaccharides, such as sucrose, are difficult to be utilized by microalgae under both heterotrophic and mixotrophic conditions. In this study, a symbiotic yeast was accidentally found in a contaminated algal suspension. The symbiotic yeast was isolated and identified as Cryptococcus sp. This yeast was able to extracellularly hydrolyze sucrose and accumulated monosaccharides in the medium. It can enhance algal growth using sucrose as the carbon source at both heterotrophic and mixotrophic modes when mix-cultured with Chlorella pyrenoidosa. The highest algal cell density of 118.8 × 10⁶ and 151.2 × 10⁶ cells/mL was achieved with a final algal percentage of 83.5 and 93.2% at heterotrophic and mixotrophic culture, respectively. Furthermore, the protein and lipid content was significantly enhanced by mix-culture C. pyrenoidosa with Cryptococcus YZU-1. The fatty acid accumulated in this co-culture system was suitable for the production of biodiesel. This symbiotic yeast solved the problem that C. pyrenoidosa cannot heterotrophically or mixotrophically utilize sucrose. A high algae density was obtained and the protein and lipid accumulation were also significantly enhanced. This study provided a novel approach for production of protein or lipid-rich biomass using sucrose or sucrose-rich wastes as the carbon source.

微藻的异养或混养培养是避免自养培养中光限制的可行替代方法。然而，只有少数几种有机碳源可用于藻类培养。双糖，如蔗糖，在异养和混养条件下都难以被微藻利用。在这项研究中，在受污染的藻类悬浮液中意外发现了一种共生酵母。共生酵母被分离并鉴定为隐球菌属。这种酵母能够在细胞外水解蔗糖并在培养基中积累单糖。当与蛋白核小球藻混合培养时，它可以在异养和混养模式下使用蔗糖作为碳源促进藻类生长. 在异养和混养培养中，最终藻类百分比分别为 83.5% 和 93.2%，最高藻细胞密度分别为 118.8 × 10 ⁶和 151.2 × 10 ^{6 个}细胞/mL。此外，蛋白和脂质含量通过混合培养C. pyrenoidosa与隐球菌YZU-1显着提高。在该共培养系统中积累的脂肪酸适合于生产生物柴油。这种共生酵母解决了C. pyrenoidosa的问题不能异养或混养利用蔗糖。获得了高藻密度，蛋白质和脂质积累也显着增强。该研究为使用蔗糖或富含蔗糖的废物作为碳源生产富含蛋白质或脂质的生物质提供了一种新方法。