Production of a novel polygalacturonic acid bioflocculant REA-11 by Corynebacterium glutamicum

The production of a novel polygalacturonic acid bioflocculant REA-11 from a newly isolated strain, Corynebacterium glutamicum CCTCC M201005, was investigated. Sucrose was chosen as a carbon source for REA-11 production. Complex nitrogen sources containing urea and an organic nitrogen compound enhanced both bacterial growth and REA-11 production, among which urea plus corn steep liquor was shown to be the most efficient combination. A cost-effective medium for REA-11 production mainly comprised 17 g/l sucrose, 0.45 g/l urea, and 5 ml/l corn steep liquor, under which conditions the flocculating activity reached 390 U/ml. The molar ratio of carbon to nitrogen (C/N) significantly affected REA-11 production, where a C/N ratio of 20:1 was shown to be the best. Interestingly, by simultaneously feeding sucrose and urea at a C/N ratio of 20:1 at 24 h of fermentation, REA-11 production (458 U/ml) was enhanced by 17% compared to the control. In a 10 l jar fermentor, lower dissolved oxygen tension was favorable for REA-11 production: a flocculating activity of 520 U/ml was achieved at a kLa of 100 h−1. REA-11 raw product is relatively thermo-stable at acidic pH ranges of 3.0–6.5. Preliminary application studies showed that REA-11 had stronger flocculating activity to Kaolin clay suspension compared to chemical flocculants. In addition, the capability of decolorizing molasses wastewater indicates the industrial potential of this novel bioflocculant.