Background and objective: Biopolymers are environmental friendly, non-toxic renewable alternatives for conventional synthetic polymers. Rice wastewater contains high biochemical and chemical oxygen demands and organic contents mainly in form of starch which can cause serious environmental problems, while, it can be used as a potentially low-cost substrate for biopolymer production. The objective of the current study was to investigate the ability of Azohydromonas lata to produce poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB-co-P3HV) from rice wastewater in a batch system.
Material and methods: Aspergillus niger was first used to hydrolyze the starch content of rice wastewater to fermentable soluble sugars. Then, the bacterium Azohydromonas lata was cultured in hydrolyzed wastewater at various C: N: P ratios to produce biopolymers. So, effects of different nitrogen and carbon sources on P (3HB) and P (3HV) contents at a C: N: P ratio of 100:4:1 were assessed.
Results and conclusion: This study showed that Azohydromonas lata was able to produce poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (P3HB-co-P3HV) from rice wastewater in the presence of simple carbon sources and under limited nutrient conditions, especially phosphorus. The highest content of P (3HB) was achieved when ammonium sulphate was used as nitrogen source at a C: N: P ratio of 100:4:1. The highest recorded cell dry mass and biopolymer concentration were 4.64 and 2.8 g l-1 respectively, at a P(3HB) content in biomass of 60% w w-1. Results indicated that phosphorus and nitrogen limitations could significantly affect P (3HB) production. In general, rice wastewater is a potential alternative for carbon sources such as glucose and maltose in polyhydroxybutyrate production.
