Proline Improves Pullulan Biosynthesis Under High Sugar Stress Condition

Pullulan is an extracellular polysaccharide produced via the fermentation of Aureobasidium pullulans. However, high sugar concentrations and hyperosmotic stress limit pullulan biosynthesis during the fermentation process. Therefore, we investigated the effects of proline supplementation on A. pullul...

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Bibliographic Details
Published in:Microorganisms (Basel) 2024-12, Vol.12 (12), p.2657
Main Authors: Liu, Keyi, Wang, Junqing, Li, Feng, Wang, Ruiming, Zeng, Qingming, Zhang, Zhenxing, Liu, Hongwei, Li, Piwu
Format: Article
Language:English
Subjects:
Amino acids
Aureobasidium pullulans
Biomass
Biosynthesis
Biotechnology
Enzymes
Fermentation
Fungi
Gluconeogenesis
Glucose
Glycerol
Glycolysis
hyperglycemia
hypertonicity
Industrial production
Metabolic pathways
Microorganisms
Physiological effects
Polysaccharides
Proline
Pullulan
Pyruvic acid
RNA sequencing
Scanning electron microscopy
Sucrose
Sugar
Sulfur
Transcriptomes
Transcriptomics
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Summary:Pullulan is an extracellular polysaccharide produced via the fermentation of Aureobasidium pullulans. However, high sugar concentrations and hyperosmotic stress limit pullulan biosynthesis during the fermentation process. Therefore, we investigated the effects of proline supplementation on A. pullulans growth and pullulan biosynthesis under high sugar and hyperosmotic stress using physiological, biochemical, and transcriptomic analyses. High sugar concentrations significantly inhibited A. pullulans growth and pullulan biosynthesis. High sugar and hyperosmotic stress conditions significantly increased intracellular proline content in A. pullulans. However, treatment with proline (400 mg/L proline) significantly increased biomass and pullulan yield by 10.75% and 30.06% (174.8 g/L), respectively, compared with those in the control group. To further investigate the effect of proline on the fermentation process, we performed scanning electron microscopy and examined the activities of key fermentation enzymes. Proline treatment preserved cell integrity and upregulated the activities of key enzymes involved in pullulan biosynthesis. Transcriptome analysis revealed that most differentially expressed genes in the proline group were associated with metabolic pathways, including glycolysis/gluconeogenesis, pyruvate metabolism, and sulfur metabolism. Conclusively, proline supplementation protects A. pullulans against high sugar and hyperosmotic stress, providing a new theoretical basis and strategy for the efficient industrial production of pullulans.
ISSN:2076-2607
DOI:10.3390/microorganisms12122657