Project description:Pseudozyma aphidis is one of the most productive microbial producers of mannosylerythritol lipids on vegetable oils with a unique product spectrum that contains all four main variants MEL-A, -B, -C and -D. Secretion of MEL is thereby accompanied by a morphologenetic switch from yeast to hyphal growth. To investigate the genetic characteristics of MEL secretion and dimorphic transition, we analyzed the transcriptome of P. aphidis during production of MEL after the morphologenetic switch. The analysis revealed that the strong activation of 4 of the 5 genes within the MEL-cluster is clearly dependent on the presence of a hydrophobic carbon source. Only the acetyltransferase mat1 is not induced. This may explain the heterogeneous mixture of MEL with different degree of acetylation. In parallel to the MEL-Cluster, we saw a significant induction of a large group of genes which are coding for cell wall modifying enzymes. These genes were mainly grouped in two large gene clusters typical for the concerted cellular switch. In addition, a group of transcription factors was activated which may be key regulator candidates for MEL-synthesis and cell development. The induction of nitrogen metabolism and assimilation processes for phosphate, iron and other nutrients draw a picture of further cellular requirements at this time point. As part of this work, we present the manually annotated and experimentally verified genome and transcriptome of P. aphidis DSM 70725 with a total number of 6942 genes. 82 % of the genes are othologs to Pseudozyma antarctica and 73 % orthologs to Ustilago maydis.
Project description:Pseudozyma aphidis is one of the most productive microbial producers of mannosylerythritol lipids on vegetable oils with a unique product spectrum that contains all four main variants MEL-A, -B, -C and -D. Secretion of MEL is thereby accompanied by a morphologenetic switch from yeast to hyphal growth. To investigate the genetic characteristics of MEL secretion and dimorphic transition, we analyzed the transcriptome of P. aphidis during production of MEL after the morphologenetic switch. The analysis revealed that the strong activation of 4 of the 5 genes within the MEL-cluster is clearly dependent on the presence of a hydrophobic carbon source. Only the acetyltransferase mat1 is not induced. This may explain the heterogeneous mixture of MEL with different degree of acetylation. In parallel to the MEL-Cluster, we saw a significant induction of a large group of genes which are coding for cell wall modifying enzymes. These genes were mainly grouped in two large gene clusters typical for the concerted cellular switch. In addition, a group of transcription factors was activated which may be key regulator candidates for MEL-synthesis and cell development. The induction of nitrogen metabolism and assimilation processes for phosphate, iron and other nutrients draw a picture of further cellular requirements at this time point. As part of this work, we present the manually annotated and experimentally verified genome and transcriptome of P. aphidis DSM 70725 with a total number of 6942 genes. 82 % of the genes are othologs to Pseudozyma antarctica and 73 % orthologs to Ustilago maydis. Experimental annotation of transcriptional landscape combined with examination of gene expression on two different carbon sources.
Project description:Mannosylerythritol lipids are glycolipid biosurfactants with many interesting properties. Despite the general interest in those molecules and the need for a robust process, studies on their production in bioreactors are still scarce. In the current study, the fermentative production of MEL in a bioreactor with Moesziomyces aphidis was performed using a defined mineral salt medium. Several kinetic process parameters like substrate consumption rates and product formation rates were evaluated and subsequently enhanced by increasing the biomass concentration through an exponential fed-batch strategy. The fed-batch approaches resulted in two to three fold increased dry biomass concentrations of 10.9-15.5 g/L at the end of the growth phase, compared with 4.2 g/L in the batch process. Consequently, MEL formation rates were increased from 0.1 g/Lh up to around 0.4 g/Lh during the MEL production phase. Thus, a maximum concentration of up to 50.5 g/L MEL was obtained when oil was added in excess, but high concentrations of residual fatty acids were also present in the broth. By adjusting the oil feeding to biomass-specific hydrolysis and MEL production rates, a slightly lower MEL concentration of 34.3 g/L was obtained after 170 h, but at the same time a very pure crude lipid extract with more than 90% MEL and a much lower concentration of remaining fatty acids. With rapeseed oil as substrate, the ideal oil-to-biomass ratio for full substrate conversion was found to be around 10 goil/gbiomass. In addition, off-gas analysis and pH trends could be used to assess biomass growth and MEL production. Finally, kinetic models were developed and compared to the experimental data, allowing for a detailed prediction of the process behavior in future experiments.
Project description:Mannosylerythritol lipids (MELs) are one of the most promising biosurfactants because of their excellent physicochemical properties, high environmental compatibility, and various biological functions. In this study, a mangrove yeast strain Moesziomyces aphidis XM01 was identified and used for efficient extracellular MEL production. The MEL titer reached 64.5 ± 0.7 g/L at flask level within 7 days with the optimized nitrogen and carbon source of 2.0 g/L NaNO3 and 70 g/L soybean oil. Furthermore, during a 10-L two-stage fed-batch fermentation, the final MEL titer reached 113.6 ± 3.1 g/L within 8 days, with prominent productivity and yield of 14.2 g·L-1·day-1 and 94.6 g/g(glucose and soybean oil). Structural analysis indicated that the produced MELs were mainly MEL-A and its fatty acid profile was composed of only medium-chain fatty acids (C8-C12), especially C10 acids (77.81%). Further applications of this compound were evaluated as one-step self-assembly nanomicelles. The obtained MEL nanomicelles showed good physicochemical stability and antibacterial activity. In addition, using clarithromycin as a model hydrophobic drug, the MEL nanomicelles exhibited high loading capacity and could be used for the controlled and sustained drug release in low-pH environments. Therefore, M. aphidis XM01 is an excellent candidate for efficient MEL production, and the prepared MEL nanomicelles have broad application prospects in the pharmaceutical and cosmetic fields.Supplementary informationThe online version contains supplementary material available at 10.1007/s42995-022-00135-0.