Utilization of lactose and whey permeate for the sustainable production of polyhydroxyalkanoates by Hydrogenophaga pseudoflava DSM1034.

Abstract

The utilization of agri-food wastes holds significant importance from both environmental and economic standpoints. Whey permeate, a by-product of cheese manufacturing with high lactose content, could be considered a promising substrate for microbial growth to yield value-added products. Whey permeate was therefore investigated as a potential feedstock for the production of polyhydroxyalkanoates (PHAs) by Hydrogenophaga pseudoflava DSM1034. Although the ability of this microorganism to grow and accumulate PHAs on whey permeate has been previously demonstrated, the PHAs yields were notably low. Therefore, a meticulous inoculum optimization was performed, taking into consideration adaptation to lactose-containing substrates, initial bacterial concentration, and growth kinetics. In media containing lactose as a carbon source, the lag phase, exceeding 40hours in non-optimized conditions, decreased to only 4hours. In whey permeate, a cell dry weight (CDW) of 5.49 ±0.08g/L was obtained. PHAs fraction in CDW and PHAs yield were 52.48±3.14% of CDW and 0.144g/g of consumed sugar, respectively. Furthermore, these results were achieved in flask without hydrolysis of lactose contained in the permeate. Moreover, no galactose remained unutilized in the spent broth demonstrating that H. pseudoflava DSM1034 metabolized both sugars contained in lactose. Additionally, in culture media containing mixtures of glucose and galactose, microbial growth was lower compared to growth on comparable amounts of lactose. This study underscores the potential of whey permeate as a valuable resource for the production of PHAs, offering a sustainable solution for the utilization of dairy industry by-products, mitigating its environmental impact and promoting sustainable resource utilization.