Transcriptome analysis of polysaccharide-based microbial flocculant MBFA9 biosynthesis regulated by nitrogen source

ABSTRACTThe industrial production of penicillin G byPenicillium chrysogenumrequires the supplementation of the growth medium with the side chain precursor phenylacetate. The growth ofP. chrysogenumwith phenylalanine as the sole nitrogen source resulted in the extracellular production of phenylacetate and penicillin G. To analyze this natural pathway for penicillin G production, chemostat cultures were switched to [U-13C]phenylalanine as the nitrogen source. The quantification and modeling of the dynamics of labeled metabolites indicated that phenylalanine was (i) incorporated in nascent protein, (ii) transaminated to phenylpyruvate and further converted by oxidation or by decarboxylation, and (iii) hydroxylated to tyrosine and subsequently metabolized via the homogentisate pathway. The involvement of the homogentisate pathway was supported by the comparative transcriptome analysis ofP. chrysogenumcultures grown with phenylalanine and with (NH4)2SO4as the nitrogen source. This transcriptome analysis also enabled the identification of two putative 2-oxo acid decarboxylase genes (Pc13g9300 and Pc18g01490). cDNAs of both genes were cloned and expressed in the 2-oxo-acid-decarboxylase-freeSaccharomyces cerevisiaestrain CEN.PK711-7C (pdc1 pdc5 pdc6Δ aro10Δ thi3Δ). The introduction of Pc13g09300 restored the growth of thisS. cerevisiaemutant on glucose and phenylalanine, thereby demonstrating that Pc13g09300 encodes a dual-substrate pyruvate and phenylpyruvate decarboxylase, which plays a key role in an Ehrlich-type pathway for the production of phenylacetate inP. chrysogenum. These results provide a basis for the metabolic engineering ofP. chrysogenumfor the production of the penicillin G side chain precursor phenylacetate.

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Biomass and Lipid Accumulation Kinetics and the Transcriptome of Oleaginous Microalga Tetradesmus Bernardii (Chlorophyceae) Under Heterotrophic Culture With Different Nitrogen Source Supply and Carbon/Nitrogen Ratio

10.21203/rs.3.rs-72257/v1 ◽

2020 ◽

Author(s):

Baoyan Gao ◽

Feifei Wang ◽

Luodong Huang ◽

Hui Liu ◽

Yuming Zhong ◽

...

Keyword(s):

Organic Carbon ◽

Nitrogen Source ◽

Batch Culture ◽

Lipid Content ◽

Transcriptome Analysis ◽

Glucose Concentration ◽

Lipid Accumulation ◽

Biofuel Production ◽

Heterotrophic Culture ◽

Time Resolved

Abstract Background: Heterotrophic cultivation of microalgae has been proposed as a viable alternative method for novel high-value biomolecules, enriched biomass and biofuel production because of their allowance of high cell density levels, as well as simple production technology. Tetradesmus bernardii, a newly isolated high-yielding oleaginous microalga under photoautotrophic conditions, is able to grow heterotrophically, meaning that it can consume organic carbon sources in dark condition. We investigated the effect of different carbon/nitrogen (C/N) ratios on the growth and lipid accumulation of T. bernardii in heterotrophic batch culture under two nitrogen sources (NaNO3, CO(NH2)2). In addition, we conducted time-resolved transcriptome analysis to reveal the metabolic mechanism of T. bernardii in heterotrophic culture. Results: T. bernardii can accumulated high biomass concentrations in heterotrophic batch culture which the highest biomass of 46.09 g/L was achieved at 100 g/L glucose concentration. The rate of glucose to biomass was exceed 55% when the glucose concentration was less than 80 g/L, and the C/N ratio was 44 at urea treatment. The culture was beneficial to lipid accumulation at a C/N ratio between 110 and 130. NaNO3 used as a nitrogen source enhanced the lipid content more than urea, and the highest lipid content was 45% of dry weight. We performed RNA-seq to analyze the time-resolved transcriptome of T. bernardii. As the nitrogen was consumed in the medium, nitrogen metabolism related genes were significantly up-regulated to speed up the N metabolic cycle. As chloroplasts were destroyed in the dark, the metabolism of cells was transferred from chloroplasts to cytoplasm. However, storage of carbohydrate in chloroplast remained active, mainly the synthesis of starch, and the precursor of starch synthesis in heterotrophic culture may largely came from the absorption of organic carbon source (glucose). With regard to lipid metabolism, the related genes of fatty acid synthesis in low nitrogen concentration increased gradually with the extension of cultivation time.Conclusion: T. bernardii exhibited rapid growth and high lipid accumulation in heterotrophic culture. It may be a potential candidate for biomass and biofuel production. Transcriptome analysis showed that multilevel regulation ensured the conversion from carbon to the synthesis of carbohydrate and lipid.

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The transcriptome analysis on urea response mechanism in the process of ergosterol synthesis by Cordyceps cicadae

Scientific Reports ◽

10.1038/s41598-021-90377-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Qihui Su ◽

Zhicai Zhang ◽

Xiaocui Liu ◽

Feng Wang

Keyword(s):

Nitrogen Source ◽

Gene Transcription ◽

Transcriptome Analysis ◽

Regulatory Element ◽

Fermentation Medium ◽

Transcription Level ◽

Go Annotation ◽

Cordyceps Cicadae ◽

Gene Transcription Level ◽

Ergosterol Synthesis

AbstractNitrogen source is required for the growth of Cordyceps cicadae and involved in the regulation of metabolite synthesis. In order to further investigate the regulatory effects of nitrogen sources on the ergosterol synthesis by C. cicadae. We first confirmed that urea could significantly increase the ergosterol synthesis. The transcriptome analysis showed that compared with biomass cultured in the control fermentation medium (CFM), 1340 differentially expressed genes (DEGs) were obtained by Gene Ontology (GO) annotation, and 312 DEGs were obtained by Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation from the biomass cultured in CFM + CO(NH2)2. Urea up-regulated D-3-phosphoglycerate dehydrogenase gene transcription level and down-regulated enolase and L-serine/L-threonine ammonialyase gene transcription level, increased serine synthesis, allosterically activate pyruvate kinase, to promote the synthesis of pyruvate and CH3CO ~ SCOA, the primer of ergosterol; Urea increase the genes transcription related with ergosterol synthesis by up-regulating the steroid regulatory element binding protein gene transcription levels. The transcriptome results were provided by those of qRT-PCR. Collectively, our finding provided valuable insights into the regulatory effect of nitrogen source on the ergosterol synthesis by C. cicadae.

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