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• A novel four-stage process was developed for PHA production from cheese whey. • Silicone membrane extraction added as a fourth stage to conventional process. • VFA extraction allowed to optimize C/N ratio for selection and accumulation stages. • A maximum PHA content of 37% was achieved by implementing the membrane extraction. This study presents a novel four-stage process for polyhydroxyalkanoates (PHA) production from nutrient-rich sheep cheese whey (CW). The key advancement was the integration of a volatile fatty acid (VFA) extraction stage into the conventional three-stage PHA production process. Application of membrane separation to fermented cheese whey resulted in the generation of a “retentate” stream containing both organic acids and nutrients, suitable for microbial culture selection, and a VFA-rich but nutrient deprived “permeate” stream, ideal for PHA accumulation. Thus, the carbon-to-nitrogen (C/N) ratio was optimized for both the selection and accumulation stages, which is crucial for efficient PHA production and for eliminating the need for exogenous nitrogen addition. The integrated process resulted in significantly higher yields (0.55 vs 0.26 g C-PHA g C-OA -1 ) and PHA content (37% vs 28%) than the control, where fermented cheese whey was directly used as feedstock for the accumulation stage. The results highlight the potential of this approach for optimizing PHA production from sub-optimal, nutrient-rich substrates.
Asunis et al. (Thu,) studied this question.