Polyhydroxyalkanoates production with Ralstonia eutropha from low quality waste animal fats

Area of Science:

• Biotechnology
• Polymer Science
• Microbial Engineering

Background:

• Polyhydroxyalkanoates (PHAs) are biodegradable polyesters offering sustainable alternatives to petroleum-based plastics.
• Ralstonia eutropha is a key microorganism for PHA biosynthesis.
• Utilizing low-cost feedstocks like waste animal fats is crucial for economic PHA production.

Purpose of the Study:

• To investigate the feasibility of using industrially rendered waste animal fats as a carbon source for PHA production by Ralstonia eutropha.
• To develop an efficient emulsification strategy for enhancing the bioavailability of solid fats.
• To evaluate PHA yield, productivity, and polymer composition using both wild-type and recombinant R. eutropha strains.

Main Methods:

• Development of an emulsification technique for solid waste animal fats without pre-treatment.
• Cultivation of wild-type R. eutropha H16 on various fats to produce polyhydroxybutyrate (PHB).
• Cultivation of a recombinant R. eutropha strain on waste fat to produce poly(hydroxybutyrate-co-hydroxyhexanoate) [P(HB-co-HHx)] in shake flasks and lab fermenters.

Main Results:

• Wild-type R. eutropha produced 79-82% PHB (w/w) per cell dry weight (CDW) on different fats, achieving 0.3g PHB/(L × h) productivity and 24 g/L total production with tallow.
• The recombinant strain yielded 49-72% PHA (w/w) per CDW with 16-27 mol% HHx content in shake flasks.
• In lab fermenters, the recombinant strain grown on low-quality waste fat achieved 45 g/L CDW, 60% PHA (w/w) per CDW, and 0.4 g PHA/(L × h) productivity with 19 mol% HHx.

Conclusions:

• Waste animal fats, even of low quality, are viable and inexpensive carbon feedstocks for PHA production.
• The developed emulsification strategy effectively improves fat bioavailability for microbial PHA synthesis.
• This approach holds significant potential for advancing the commercialization of sustainable PHA bioplastics.