Non-sugar-based Bioprocess for P(3HB) Production: Combining Methanotrophs and Mealworms

M. Lackner, I. Zainab-L. and K. Sudesh

Abstract
The bioeconomy today relies mostly on sugar and physicochemical extraction processes, which limit both cost reduction and scale-up potential, yet these two aspects are vital for the market success of circular bioeconomy products. Gas fermentation is a platform technology that utilizes all kinds of waste biomass streams through low-cost, clean, and well-defined gaseous substrates. It can be used to obtain bioplastics. In this work, methane (CH4) was subjected to methanotrophic conversion by Methylocystis sp. GB 25. The freeze-dried bacterial biomass containing 47 wt% P(3HB) – poly(3-hydroxybutyrate), was subsequently fed to mealworms. The cells were fully consumed, and the P(3HB) granules were recovered within 24 h. The final PHB purity obtained was 95 % through a simple purification step. This work demonstrated that a simple bioprocess for biopolymer extraction can be applied to small bacterial cells like methanotrophs, offering a viable alternative to classic downstream processing steps such as chlorinated solvent extraction. The methanotrophic PHB was found to exhibit high molecular weight, making it an interesting biobased, biodegradable polymer.

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Keywords
sustainable feedstock, green downstream processing, extraction, bioplastics, biopolymers