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Impact of saline osmotic stress on halotolerant polyhydroxyalkanoate (PHA)-accumulating mixed microbial cultures
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Resumo(s)
Bioconversion of saline organic side-streams into value-Added products, such as polyhydroxyalkanoates (PHAs), can reduce treatment costs and contribute to a circular economy. PHA production by Mixed Microbial Cultures (MMC) under saline conditions enables the use of salty side-streams and seawater (∼3.5-w/v NaCl) as process water, further enhancing the economic and environmental sustainability of the process, particularly for industries located at coastal sites. This study investigates a strategy to further improve the PHA production capacity of PHA-Accumulating MMC selected under near seawater salinity. Specifically, the selected culture was evaluated for its PHA production capacity under sudden osmotic imbalances by subjecting it to osmotic downshock (30-0-gNaCl/L) and upshock (30-60-gNaCl/L). The culture was enriched under double selective pressure (F/f regime and uncoupled C/N feeding) at 30 gNaCl/L, leading to the dominance of Neptunomonas phycophila (79.7-). During PHA accumulation, a maximum PHA content of 42.4-wt. was achieved, with a resulting P(3HB-co-3HV) copolymer containing 45-wt. 3HV. Osmotic downshock (<30 gNaCl/L) resulted in a 1.4-fold increase in PHA content (56.9 %) and storage yield compared to the control (30 gNaCl/L), while high osmotic upshock (60 gNaCl/L) had a negative effect. Additionally, varying food-To-microorganism (F/M) ratios and saline concentrations allowed the production of polymers with varying 3HB monomeric content (53-to 72 %), expanding the potential applications of these polymers.
Descrição
Funding Information:
The authors are thankful for the financial support provided by the FCT - Fundação para a Ciência e a Tecnologia, I.P. (SaltiPHA project: PTDC/BTA-BTA/30902/2017, Research Unit on Applied Molecular Biosciences – UCIBIO: UIDP/04378/2020 (DOI: 10.54499/UIDP/04378/2020) and UIDB/04378/2020 (DOI: 10.54499/UIDB/04378/2020), Associate Laboratory Institute for Health and Bioeconomy - i4HB: LA/P/0140/2020 (DOI: 10.54499/LA/P/0140/2020)). Matteo Grana acknowledges Gruppo CAP for funding the PhD scholarship. The authors also acknowledge Elsa Mora and Elisabete Freitas for assistance with chemical analysis.
Publisher Copyright:
© 2025 The Authors.
Palavras-chave
Biodegradable biopolymer Osmotic pressure P(3HB-co-3HV) Reduce costs Saline resources Transient salinity Chemical Engineering (miscellaneous) Waste Management and Disposal Pollution Process Chemistry and Technology SDG 8 - Decent Work and Economic Growth SDG 12 - Responsible Consumption and Production