A four-microorganism three-step fermentation process for producing medium-chain-length polyhydroxyalkanoate from...

Area of Science:

• Biotechnology
• Polymer Science
• Microbial Fermentation

Background:

• Polyhydroxyalkanoates (PHAs) are biodegradable polyesters with diverse applications.
• Starch, a readily available biopolymer, presents a sustainable feedstock for bioproducts.
• Efficient microbial production of medium-chain-length PHAs (mcl-PHAs) remains a challenge.

Purpose of the Study:

• To develop a novel microbial fermentation process for mcl-PHA production using starch as the sole carbon source.
• To establish a feasible strategy for converting kitchen waste into valuable mcl-PHA.

Main Methods:

• A three-step fermentation process involving four specific microorganisms: *Aspergillus niger*, *Saccharomyces cerevisiae* L2612, *Acetobacter orientalis*, and *Pseudomonas putida* KT2440-acs.
• Starch was used as the initial carbon source at a concentration of 30 g/L.
• Fermentation was monitored for glucose, acetic acid, and final mcl-PHA production over 144 hours.

Main Results:

• The process achieved a final mcl-PHA output of 0.5 g/L with an overall productivity of 3.47 mg/(L·h).
• The total starch to mcl-PHA yield was 16.67 mg/g.
• Intermediate concentrations of glucose (17.66 g/L at 48 h) and acetic acid (2.36 g/L at 96 h) were observed.

Conclusions:

• This study represents the first attempt to produce mcl-PHA directly from starch.
• The developed process provides a viable strategy for producing mcl-PHA from starch, with potential applications for kitchen waste valorization.
• A defined microbial consortium and a relatively short fermentation cycle were achieved for mcl-PHA production.