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 1H 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.