Abstract:
Plastic and industrial wastewater are among the biggest ecological threats in the modern era. Advanced wastewater management using microorganisms can not only reduce environmental pollutions, but also assist in the production of valuable products, such as biodegradable biopolymers. It has been reported that certain microbes have the capability of accumulating a significant amount of biopolymers intracellularly. Lactose in the cheese whey, a potential ecological hazard, is a high-quality carbon substrate for microbes that can up-cycle lactose into valuable products. For example, Halophiles are a class of microbes which survive and thrive in saline environments. It will be a win-win to use Halophiles to treat high salinity cheese whey while converting lactose into biopolymers. Nitrate pollution in water sources causes waterway eutrophication among many another environmental concerns. Nitrate concentrations in wastewater plants could be reduced by using microbial denitrification approaches.
In the current research, the ability of some halophilic, autotroph hydrogenotrophic stains to produce polyhydroxyalkanoate, a biopolymer, was investigated. Also, heterotrophic halophiles that can use lactose to reduce nitrate/nitrite and accumulate PHA were explored.
Pure culture experiments were carried out in the presence of lactose by the Oleiagrimonas soli strain and in the presence of nitrate-containing salts by Rhodobacteraceae-CCB-MM2 and Rhodocyclaceae_Thauera strains. Mixed culture studies were performed anaerobically in an aqueous medium by Rhodobacteraceae-CCB-MM2, and Rhodocyclaceae_Thauera strains in the presence of a hydrogen/carbon dioxide/nitrogen atmosphere.
Pure culture studies were not successful due to the prolonged starvation of the bacteria. During the first six hours of the mixed culture studies, no bacterial growth or PHA formation could be observed. However, after a prolonged lag phase of 24-30 hours, the OD600 and OD312 increased, indicating cell growth and PHA accumulation.
Mixed culture studies with autotroph hydrogenotrophic microbes in the presence of hydrogen and carbon dioxide as the carbon source showed the potential of producing PHA, albeit with a prolonged lag phase.