Novel spectrophotometric method for detection and estimation of butanol in acetone–butanol–ethanol fermenter

A new, simple, rapid and selective spectrophotometric method has been developed for detection and estimation of butanol in fermentation broth. The red colored compound, produced during reduction of diquat-dibromide-monohydrate with 2-mercaptoethanol in aqueous solution at high pH (>13), becomes purple on phase transfer to butanol and gives distinct absorption at λ520nm. Estimation of butanol in the fermentation broth has been performed by salting out extraction (SOE) using saturated K3PO4 solution at high pH (>13) followed by absorbance measurement using diquat reagent. Compatibility and optimization of diquat reagent concentration for detection and estimation of butanol concentration in the fermentation broth range was verified by central composite design. A standard curve was constructed to estimate butanol in acetone–ethanol–butanol (ABE) mixture under optimized conditions. The spectrophotometric results for butanol estimation, was found to have 87.5% concordance with the data from gas chromatographic analysis. Spectrophotometric estimation of butanol in ABE fermenter selectively in presence of ethanol acetone and other metabolites has been performed by salting out extraction (SOE) using saturated K3PO4 solution, an excellent salting out extractant as well as dyeing agent, at high pH (>13), followed by absorbance measurement using diquat reagent (reduced diquat) in real system by Clostridium beijerinckii B-592. [Display omitted] •Screening of salts for efficient salting out extraction.•Selection diquat as a reagent for detection of butanol.•Investigation of metabolites production using Clostridium beijerinckii B-592.•New, simple, rapid and selective spectrophotometric estimation of butanol in fermenter.