Evaluation of halomonas campaniensis as a platform for producing biotechnological compounds from agro-industrial waste

Abstract

The generation of biotechnological products represents an alternative to many chemical-based processes, although they might have high costs and contribute to general pollution. For this reason, it is relevant to find non-conventional extremophile microorganisms, such as the genre Halomonas, that can grow in high salinity or extreme pH, and to be able to grow using waste treams for circular bioeconomy. Particularly, H. campaniensis can produce polyhydroxybutyrate (PHB), a biodegradable polymer with the potential to replace conventional plastics. The objective of this study is to evaluate the performance of H. campaniensis to generate biomass and PHB using alternative substrates (urea as nitrogen source and orange peel residues for carbon source). First, a contrast between the use of yeast extract and urea was performed to determine optimal urea concentration. Then, a range of concentrations of orange peel hydrolysate were employed (10% to 100% v/v) to monitor biomass and PHB production through time. Results show that the use of urea (4 g/L) to replace yeast extract (5 g/L) from LB media is a viable and more cost-effective alternative, with both achieving the same level of biomass. Regarding the growth in orange peel-based media, biomass from LB and this new media achieved a comparable level in less time. The production of PHB was shown to achieve a maximum concentration at 24 hours after inoculation. Overall, the highest biomass production was obtained whenusing 40% hydrolysate concentration for 24 hours. In contrast, the highest PHB yield was achieved at 60% hydrolysate concentration after 24 hours. Additionally, this work established and optimized a highly efficient transformation protocol for H. campaniensis, enabling future genetic engineering efforts to improve PHB production or introduce new metabolic pathways. These results demonstrate the potential of H. to convert orange peel waste into PHB efficiently, contributing to the circular economy by converting agro-industrial residues into high-value products while reducing environmental impact.