Cheese whey mother liquor as dairy waste with potential value for polyhydroxyalkanoate production by extremophilic Paracoccus homiensis

Abstract

The production of scl-polyhydroxyalkanoates homopolymers and heteropolymers by Paracoccus homiensis was investigated using cheese whey mother liquor (CWML) and cheese whey (CW). Our results showed that the analyzed strain was able to convert waste streams of dairy processing into biopolymers, reaching a maximum of 3.3 ± 0.31 g/L of cell dry mass (CDM) with 1.1 g/L of P(3HB-co-3 HV) copolymer (29.0% of CDM) at 72 h. CWML was the preferred substrate to achieve a high level of PHAs. Moreover, our data suggested that PHA content in the analyzed bacterial cells was stimulated by nitrogen deficiency when CWML was used. Whereas nutrients limitation did not enhance the PHA concentration in the cultivations supplmented with CW. We proved that the monomeric composition of extracted PHAs depended on the type of substrate, its concentration supplied and the culture media composition. Detailed characterization of the extracted PHAs biofilms using a differential scanning calorimetric, thermogravimetric and water contact angle analysis proved that they have useful material properties suitable for various applications. PHA production on dairy waste by Paracoccus species has not been reported so far. Taking into account the positive aspects of employing extremophiles in industrial biotechnology, Paracoccus homiensis is a very interesting halophilic bacterium for PHA production using cheese manufacturing wastes. Valorizing cheese whey mother liquor as the PHA production feedstock would be an excellent dairy processing waste management strategy.