Advantage of Using Retentate in Polyhydroxybutyrate (PHB) Production from Sugarcane Juice

Membrane filtration of sugarcane juice is a green technology with great development potential. The technology does not involve the use of chemical additives. Thus, the permeate without chemical residues can be obtained to produce high-quality sugar. However, retentate is a by-product produced by the ceramic membrane clarification process of sugarcane juice. The cost-effective treatment of retentate is the key industrial application of membrane technology in the sugar industry. The current study evaluated the microbial treatment of retentate. A wild PHB-producing strain was isolated from river sludge and designated as Bacillus aryabhattai S2 by 16S rRNA gene sequencing. The extract of B. aryabhattai S2 was characterized by GC–MS, FTIR, and 1 H NMR. HPLC was used to detect the content of sugar (12 mg/mL) in the retentate. PHB was produced by shaking flask fermentation with the retentate as the carbon source. PHB yield from retentate was 2.831 g/L, which was four times higher than PHB yield from glucose (0.647 g/L). The use of the retentate for the production of polyhydroxybutyrate by B. aryabhattai S2 was promising. In addition to provide carbon source, the retentate also provides 16% water for the fermentation system, thereby saving on water resources for the duration of the fermentation.