Enhancement of sophorolipids production in Candida batistae, an unexplored sophorolipids producer, by fed-batch fermentation

Sophorolipids (SLs) from Candida batistae has a unique structure that contains ω-hydroxy fatty acids, which can be used as a building block in the polymer and fragrance industries. To improve the production of this industrially important SLs, we optimized the culture medium of C. batistae for the first time. Using an optimized culture medium composed of 50 g/L glucose, 50 g/L rapeseed oil, 5 g/L ammonium nitrate and 5 g/L yeast extract, SLs were produced at a concentration of 24.1 g/L in a flask culture. Sophorolipids production increased by about 19% (28.6 g/L) in a fed-batch fermentation using a 5 L fermentor. Sophorolipids production more increased by about 121% (53.2 g/L), compared with that in a flask culture, in a fed-batch fermentation using a 50 L fermentor, which was about 787% higher than that of the previously reported SLs production (6 g/L). These results indicate that a significant increase in C. batistae-derived SLs production can be achieved by optimization of the culture medium composition and fed-batch fermentation. Finally, we successfully separated and purified the SLs from the culture medium. The improved production of SLs from C. batistae in this study will help facilitate the successful development of applications for the SLs.

De novo biosynthesis of 8-hydroxyoctanoic acid via a medium-chain length specific fatty acid synthase and cytochrome P450 in Saccharomyces cerevisiae

Terminally hydroxylated fatty acids or dicarboxylic acids are industrially relevant compounds with broad applications. Here, we present the proof of principle for the de novo biosynthesis of 8-hydroxyoctanoic acid from glucose and ethanol in the yeast Saccharomyces cerevisiae. Toxicity tests with medium-chain length ω-hydroxy fatty acids and dicarboxylic acids revealed little or no growth impairments on yeast cultures even at higher concentrations. The ability of various heterologous cytochrome P450 enzymes in combination with their cognate reductases for ω-hydroxylation of externally fed octanoic acid were compared. Finally, the most efficient P450 enzyme system was expressed in a yeast strain, whose fatty acid synthase was engineered for octanoic acid production, resulting in de novo biosynthesis of 8-hydroxyoctanoic acid up to 3 ​mg/l. Accumulation of octanoic acid revealed that cytochromes P450 activities were limiting 8-hydroxyoctanoic acid synthesis. The hydroxylation of both externally added and intracellularly produced octanoic acid was strongly dependent on the carbon source used, with ethanol being preferred. We further identified the availability of heme, a cofactor needed for P450 activity, as a limiting factor of 8-hydroxyoctanoic acid biosynthesis.

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Low toxic effects of medium-chain ω-hydroxy fatty acids on yeast cells .

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Systematic comparison of cytochrome P450 enzyme activities on octanoic acid .

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De novo biosynthesis of 8-hydroxyoctanoic acid .

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Improvement of cytochrome P450 activity with ethanol or by addition of hemin .

Enzymatic cascade biosynthesis reaction of musky macrolactones from fatty acids

Musky macrolactones are an important group of compounds used in high-valued perfumery. An enzymatic cascade reaction including cytochrome P450 hydroxylase and lipase was explored to biosynthesize musky macrolactones. Firstly, fatty acids were hydroxylated by P450 hydroxylase to produce the corresponding ω-hydroxy fatty acids. Then ω-hydroxy fatty acids were lactonized by lipase. ω-Hydroxy fatty acids can difficultly be synthesized by traditional chemical methods, and the production of these compounds were key constraint factors during the whole reaction. To obtain enough precursors of macrolactones, an efficient production of ω-hydroxy fatty acids was explored. A mutant of P450 BM3 from Bacillus megaterium was used as terminal hydroxylases. To improve the yield of ω-hydroxy fatty acids, the coenzyme regeneration system and auxiliary organic solvent were optimized. The conversion using the P450 BM3 mutant under the biphase system was up to 42% towards ω-hydroxy pentadecanoic acid and 98% towards ω-hydroxy palmitic acid. The results reveal that the musky macrolactones, exaltolide and silvanone supra, could be synthesized in the hydroxylation-lactonization cascade reaction. Finally, 81 mg of exaltolide was obtained from 242 mg pentadecanoic acid, and 199 mg of silvanone supra from 256 mg palmitic acid.

Structural profiling of wax biopolymer from Pinus roxburghii Sarg. needles using spectroscopic methods

Pinus roxburghii Sarg. is the most abundant species in Himalayan region. The needles of the species largely contribute to the forest biomass and remain the major cause of forest fires leading to climate change, biodiversity loss, etc. Intriguingly, the layer of needles contains wax, a biomacromolecule with potential chemical functionalities for value addition. In the present study, a distinctive approach towards complete structural analysis of the isolated wax in its native state has been done using ¹H, ¹³C, HSQC, HMBC, COSY, TOCSY along with GC-MS of the methyl esters of constituent fatty acids. The wax was isolated in a quantitative yield of 1.64% and analyses suggest that it is a polymer of linearly attached fatty acid esters which on hydrolysis yielded three types of ω-hydroxy fatty acids viz. 12-hydroxydodecanoic acid, 14-hydroxytetradecanoic acid and 16-hydroxyhexadecanoic acid in a ratio of 1:1:2 respectively. Complete assignments for a carbonyl group, α-, β- and other methylenes present in wax were achieved; corroborating the presence of polyester. In particular, identification of wax structure was accomplished through NMR; thereby providing a lead towards future structural analysis of waxes in their native form. The study would also be helpful to generate commercially important compounds derived from pine needle wax. This will offer an opportunity for utilisation of pine needle biomass: a root cause of Himalayan forest fires.