Bacterial production of polyhydroxyalkanoates (PHAs) using various waste carbon sources

Area of Science:

• Biotechnology and microbial engineering
• Polymer science and materials engineering
• Environmental science and sustainability

Background:

• Synthetic plastics pose environmental challenges due to their non-biodegradable nature.
• Biodegradable plastics, such as polyhydroxyalkanoates (PHAs), offer a sustainable alternative.
• High production costs of PHAs are linked to expensive carbon substrates.

Purpose of the Study:

• To investigate the cost-effective production of PHAs using waste carbon sources.
• To evaluate PHA yield from different bacterial strains utilizing rice bran and sugarcane molasses.
• To optimize PHA biosynthesis conditions for enhanced yield and efficiency.

Main Methods:

• Cultivation of bacterial strains (Bacillus subtilis, Bacillus cereus, Alcaligenes sp., Pseudomonas aeruginosa) using rice bran and sugarcane molasses as carbon sources.
• PHA production screening using Sudan Black-B stain.
• Quantification of PHA yield, cell dry mass (CDM), and PHA content.
• Analysis of biopolymer properties using Fourier Transform Infrared Spectroscopy (FTIR) and Differential Scanning Calorimetry (DSC).

Main Results:

• Pseudomonas aeruginosa achieved the highest PHA yield (93.7%) with rice bran and (95%) with sugarcane molasses.
• Sugarcane molasses resulted in the maximum PHA yield compared to rice bran across all tested bacterial strains.
• Optimal incubation times varied by bacterial strain, ranging from 24-48 hours for B. subtilis and B. cereus, and 48-96 hours for Alcaligenes sp. and P. aeruginosa.
• FTIR and DSC analyses confirmed the identity and thermal stability of the produced poly-3-hydroxybutyrate (P(3HB)).

Conclusions:

• Waste carbon sources, particularly sugarcane molasses, can be effectively utilized for cost-efficient PHA production.
• Specific bacterial strains, like P. aeruginosa and Alcaligenes sp., demonstrate high potential for industrial-scale PHA biosynthesis.
• This research supports the development of sustainable and biodegradable plastic alternatives, mitigating environmental pollution.