Production and Optimization of Polyhydroxyalkanoates (PHAs) by Corynebacterium Variabile M11: A Newly Reported PHAs-Producing Bacterium

Authors

• Mary S. Khalil, Department of Botany and Microbiology, Faculty of Science, Cairo University, 12613, Giza, EgyptFollow
• Mariam K. M. Zarif, Department of Botany and Microbiology, Faculty of Science, Cairo University, 12613, Giza, Egypt AND Department of Basic Science, Microbiology, Faculty of Oral and Dental Medicine, Future University in Egypt (FUE), New Cairo 1, 11835, Cairo, EgyptFollow
• Mahmoud S. M. Mohamed, Department of Botany and Microbiology, Faculty of Science, Cairo University, 12613, Giza, Egypt AND Department of Biology, College of Science in Yanbu, Yanbu Governorate, Taibah University, Al Madinah, Saudi ArabiaFollow

Abstract

Polyhydroxyalkanoates are a family of biopolymers that accumulate inside microorganisms as primary storage polymers in response to nutrient stress. This family of biopolymers can be used as bioplastics instead of synthetic plastics because it biodegrades into CO₂ and H₂O. This study aimed to isolate a new bacterial strain that can accumulate PHAs when cultured under unbalanced nutrient conditions of excess carbon and a depleted nitrogen source. Screening for PHAs accumulating bacterial isolates was based on culturing the bacteria on minimal salt medium containing Nile red as a fluorescent dye. Positive PHAs bacterial colonies displayed bright orange fluorescence under ultraviolet light while PHA- negative isolates failed to exhibit fluorescence. Extraction of PHAs was achieved using a dispersion of sodium hypochlorite-chloroform solution and quantified by conversion into crotonic acid through boiling in concentrated sulfuric acid and measured by UV spectrophotometer at 235 nm. The most potent isolate was selected to optimize cell growth and PHAs production conditions using the ``one- factor-at-a-time'' method. The newly isolated strain Corynebacterium variabile M11 was identified using the 16S rRNA gene and characterized as a positive PHAs-accumulating bacterium using staining and fluorescent tests. Granules were observed inside the cytoplasm by (TEM). The structure of extracted PHAs was analyzed by FTIR and 1H-NMR spectroscopy, and the results confirmed the similarity with standard PHAs and were characterized as poly(3-hydroxybutyrate-co-3- hydroxyvalerate). The optimum pH, temperature, and incubation period for maximum PHA production using dextrose and ammonium chloride were 7, 30 °C, and 72 h, respectively.

Keywords

Crotonic acid, Corynebacterium variable M11, 1H-NMR, Nile red, Polyhydroxyalkanoates

Subject Area

Biology

Article Type

Article

First Page

3438

Last Page

3453

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

How to Cite this Article

Khalil, Mary S.; Zarif, Mariam K. M.; and Mohamed, Mahmoud S. M. (2026) "Production and Optimization of Polyhydroxyalkanoates (PHAs) by Corynebacterium Variabile M11: A Newly Reported PHAs-Producing Bacterium," Baghdad Science Journal: Vol. 23: Iss. 10, Article 1.
DOI: https://doi.org/10.21123/2411-7986.5420