Related Experiment Video
Updated: Mar 16, 2026
A Tandem Liquid Chromatography–Mass Spectrometry-based Approach for Metabolite Analysis of Staphylococcus aureus
Published on: March 28, 2017
Effects of nitrogen availability on polymalic acid biosynthesis in the yeast-like fungus Aureobasidium pullulans
Yongkang Wang1, Xiaodan Song1, Yongjun Zhang2
1College of Pharmaceutical Sciences, Chongqing Engineering Research Center for Pharmaceutical Process and Quality Control, Southwest University, 2 Tian Sheng Road, Beibei, Chongqing, 400715, People's Republic of China.
Background:
Polymalic acid (PMA) is a novel polyester polymer that has been broadly used in the medical and food industries. Its monomer, L-malic acid, is also a potential C4 platform chemical. However, little is known about the mechanism of PMA biosynthesis in the yeast-like fungus, Aureobasidium pullulans. In this study, the effects of different nitrogen concentration on cell growth and PMA biosynthesis were investigated via comparative transcriptomics and proteomics analyses, and a related signaling pathway was also evaluated.
Results:
A high final PMA titer of 44.00 ± 3.65 g/L (49.9 ± 4.14 g/L of malic acid after hydrolysis) was achieved in a 5-L fermentor under low nitrogen concentration (2 g/L of NH4NO3), which was 18.3 % higher yield than that obtained under high nitrogen concentration (10 g/L of NH4NO3). Comparative transcriptomics profiling revealed that a set of genes, related to the ribosome, ribosome biogenesis, proteasome, and nitrogen metabolism, were significantly up- or down-regulated under nitrogen sufficient conditions, which could be regulated by the TOR signaling pathway. Fourteen protein spots were identified via proteomics analysis, and were found to be associated with cell division and growth, energy metabolism, and the glycolytic pathway. qRT-PCR further confirmed that the expression levels of key genes involved in the PMA biosynthetic pathway (GLK, CS, FUM, DAT, and MCL) and the TOR signaling pathway (GS, TOR1, Tap42, and Gat1) were upregulated due to nitrogen limitation. Under rapamycin stress, PMA biosynthesis was obviously inhibited in a dose-dependent manner, and the transcription levels of TOR1, MCL, and DAT were also downregulated.
Conclusions:
The level of nitrogen could regulate cell growth and PMA biosynthesis. Low concentration of nitrogen was beneficial for PMA biosynthesis, which could upregulate the expression of key genes involved in the PMA biosynthesis pathway. Cell growth and PMA biosynthesis might be mediated by the TOR signaling pathway in response to nitrogen. This study will help us to deeply understand the molecular mechanisms of PMA biosynthesis, and to develop an effective process for the production of PMA and malic acid chemicals.
Insights
Low nitrogen levels boost polymalic acid (PMA) production in Aureobasidium pullulans by upregulating key biosynthetic genes. This discovery, potentially mediated by the TOR signaling pathway, enhances understanding and production of PMA and malic acid.
Area of Science:
- Biotechnology
- Microbial biosynthesis
- Polymer science
Background:
- Polymalic acid (PMA), a novel polyester, is utilized in medical and food industries.
- L-malic acid, the monomer of PMA, is a potential C4 platform chemical.
- PMA biosynthesis mechanisms in Aureobasidium pullulans remain largely unelucidated.
Purpose of the Study:
- Investigate the impact of varying nitrogen concentrations on PMA biosynthesis and cell growth.
- Elucidate the molecular mechanisms governing PMA production in A. pullulans.
- Evaluate the role of the TOR signaling pathway in nitrogen-mediated regulation of PMA synthesis.
Main Methods:
- Comparative transcriptomics and proteomics analyses to profile gene and protein expression.
- Fermentation experiments in a 5-L fermentor to optimize PMA production.
- Quantitative reverse transcription PCR (qRT-PCR) to validate gene expression levels.
- Rapamycin stress assays to assess the TOR pathway's influence.
Main Results:
- A high PMA titer of 44.00 g/L was achieved under low nitrogen conditions (2 g/L NH4NO3), an 18.3% increase compared to high nitrogen (10 g/L NH4NO3).
- Transcriptomic analysis revealed significant differential gene expression related to ribosome, proteasome, and nitrogen metabolism under varying nitrogen availability, potentially regulated by the TOR pathway.
- Upregulation of key PMA biosynthetic genes (GLK, CS, FUM, DAT, MCL) and TOR signaling pathway components (GS, TOR1, Tap42, Gat1) was observed under nitrogen limitation.
- Rapamycin treatment inhibited PMA biosynthesis in a dose-dependent manner, downregulating TOR1, MCL, and DAT expression.
Conclusions:
- Nitrogen concentration critically regulates cell growth and PMA biosynthesis in A. pullulans.
- Low nitrogen levels are conducive to enhanced PMA production by upregulating essential biosynthetic genes.
- The TOR signaling pathway likely mediates cellular responses to nitrogen availability, influencing both growth and PMA biosynthesis.
- Findings provide a foundation for optimizing PMA and malic acid production processes.
Related Concept Videos
01:29Amino Acid Biosynthetic Pathways
01:22Inorganic Nitrogen Assimilation
01:18Amino Acid Catabolism
01:24Biosynthesis in Bacteria
02:11The Roles of Bacteria and Fungi in Plant Nutrition
01:23Stringent Response in E. coli