ABSTRACT
Sterols are crucial functional components for eukaryotic cell membrane. Due to versatile activities, sterols show wide applications in food and pharmaceutical industries. Ergosterol not only reflects cell growth but also serves as the precursor for manufacturing steroid drugs. To date, the ergosterol biosynthetic pathway in yeast has been reported, and the industrial production of ergosterol is achieved by yeast fermentation or extraction from fungal mycelia. Here, we summarize its biosynthesis, regulation, transportation, and subcellular location of enzymes in yeast. In particular, we review the regulation of ergosterol biosynthesis at transcriptional, translational and post-translational levels. Furthermore, we advocate metabolic engineering and fermentation strategies for high-level production of ergosterol. This study may provide evaluable insights into metabolic engineering of yeast for scaled-up fermentation production of ergosterol or beyond.
Subject(s)
Ergosterol/biosynthesis , Yeasts/metabolism , Bioreactors/microbiology , Candida albicans/metabolism , Cryptococcus neoformans/metabolism , Fermentation , Metabolic Engineering , Saccharomyces cerevisiae/metabolism , Schizosaccharomyces/metabolismABSTRACT
Lipase from Candida sp. 99-125 was immobilized by physical adsorption onto macroporous resins. The results showed that the nonpolar resin NKA was the best carrier used in low aqueous media. 98.98% of degree of immobilization can be achieved when the adsorption procedure was performed in the presence of heptane. The hydrolytic activity and the apparent activity recovery of lipase adsorbed on resin in heptane was 4.07 and 3.43 times higher than that of lipase adsorbed in sodium phosphate buffer, respectively. The catalytic properties of immobilized lipase for production of biodiesel in low aqueous media were studied. Immobilized lipase displayed the highest activity when the crude enzyme/resin weight ratio was 1.92:1 and the water content(water/oil weight ratio) was 15% at 40 degrees C under pH 7.4. As lipase was adsorbed on NKA in heptane to produce biodiesel, the batch conversion rate can reach 97.3% when a three-step methanolysis protocol was used. After 19 consecutive batches, the conversion rate remained 70.2%.
