End-product conversion, low product concentration and large volumes of fermentation broth, the requirements for large bioreactors, in addition to the high cost involved in generating the steam required to distil fermentation products from the broth largely contributed to the decline in fermentative products. These considerations have motivated the study of organic extractants as a means to remove the product during fermentation and minimize downstream recovery. The aim of this study is to assess the practical applicability of liquid-liquid extraction in 2,3-butanediol fermentations. Eighteen organic solvents were screened to determine their biocompatibility, and bioavailability for their effects on Klebsiella pneumoniae growth. Candidate solvents at first were screened in shake flasks for toxicity to K. pneumoniae. Cell density and substrate consumption were used as measures of cell toxicity. The possibility of employing oleyl alcohol as an extraction solvent to enhance end product in 2,3-butanediol fermentation was evaluated. Fermentation was carried out at an initial glucose concentration of 80 g/l. Oleyl alcohol did not inhibit the growth of the fermentative organism. 2,3-Butanediol production increased from 17.9 g/l (in conventional fermentation) to 23.01 g/l (in extractive fermentation). Applying oleyl alcohol as the extraction solvent, about 68% of the total 2,3-butanediol produced was extracted.
The purification of a desired protein from the complex mixture of biomolecules in a fermentation broth is one of the main challenges in industrial-scale biotechnological processes. For partial purification of industrial enzymes, one possible approach is to use aqueous two-phase extraction (APTE) as a primary downstream processing step. In the present study, the feasibility of utilizing ATPE for the purification of lipase from Rhizopus microsporus fermentation culture was investigated. The effects of the phase composition and salt type, molecular weight of the polyethylene glycol (PEG), pH of the system, sample loading and addition of neutral salts on lipase partitioning were investigated at 24 C. In most of the examined aqueous two-phase systems (ATPSs), lipase showed affinity to the top phase. Optimum conditions for lipase purification were obtained in 20% PEG 2000/12% (NH 4 ) 2 SO 4 , with 5% Na 2 CO 3 addition at pH D 8 for 30% crude load. For the optimized ATPS, the recovery yield and purification factor in the top phase were determined to be 92.3% and 19.8, respectively.
Optimal operating parameters of 2,3-Butanediol production using Klebsiella oxytoca under submerged culture conditions are determined by using Taguchi method. The effect of different factors including medium composition, pH, temperature, mixing intensity, and inoculum size on 2,3-butanediol production was analyzed using the Taguchi method in three levels. Based on these analyses the optimum concentrations of glucose, acetic acid, and succinic acid were found to be 6, 0.5, and 1.0 (% w/v), respectively. Furthermore, optimum values for temperature, inoculum size, pH, and the shaking speed were determined as 37°C, 8 (g/L), 6.1, and 150 rpm, respectively. The optimal combinations of factors obtained from the proposed DOE methodology was further validated by conducting fermentation experiments and the obtained results revealed an enhanced 2,3-Butanediol yield of 44%.
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