Application of the solid-state fermentation process and its variations in PHA production: a review

Area of Science:

• Biotechnology
• Microbial Fermentation
• Biopolymer Production

Background:

• Solid-state fermentation (SSF) offers a sustainable route for utilizing agro-industrial by-products as carbon sources.
• Production of polyhydroxyalkanoates (PHAs) via fermentation is an area of growing interest for bioplastics.
• Limited research compares SSF with submerged fermentation (SmF) for PHA synthesis.

Purpose of the Study:

• To review and compare methodologies for PHA production using SSF, SmF, or combined approaches.
• To evaluate the efficiency of different microorganisms and fermentation strategies for PHA yield and productivity.
• To identify research gaps and suggest future directions in SSF for PHA production.

Main Methods:

• Literature review of studies employing SSF, SmF, or sequential SSF-SmF for PHA production.
• Analysis of PHA yields and productivities reported for various microbial strains and substrates.
• Comparison of different fermentation process designs and their impact on PHA accumulation.

Main Results:

• Highest PHA yields (up to 86.2%) were achieved by combining SSF (hydrolysis) and SmF (production) using Cupriavidus necator.
• Bacillus species demonstrated the highest PHA yields (up to 62%) in SSF-only processes.
• High PHA percentage did not always correlate with high biomass productivity; C. necator is not optimal for SSF alone.

Conclusions:

• Combining SSF and SmF is a promising strategy for maximizing PHA yields.
• Further research is needed on scaling SSF processes and standardizing results for better comparison.
• Co-culturing C. necator with Bacillus species may enhance PHA production in SSF systems.