EFFECT OF FERMENTATION PARAMETERS ON BIO-ALCOHOLS PRODUCTION FROM GLYCEROL USING IMMOBILIZEDClostridium pasteurianum: AN OPTIMIZATION STUDY

Abstract

This article addresses the issue of effect of fermentation parameters for conversion of glycerol (in both pure and crude form) into three value-added products, namely, ethanol, butanol, and 1,3-propanediol (1,3-PDO), by immobilized Clostridium pasteurianum and thereby addresses the statistical optimization of this process. The analysis of effect of different process parameters such as agitation rate, fermentation temperature, medium pH, and initial glycerol concentration indicated that medium pH was the most critical factor for total alcohols production in case of pure glycerol as fermentation substrate. On the other hand, initial glycerol concentration was the most significant factor for fermentation with crude glycerol. An interesting observation was that the optimized set of fermentation parameters was found to be independent of the type of glycerol (either pure or crude) used. At optimum conditions of agitation rate (200 rpm), initial glycerol concentration (25 g/L), fermentation temperature (30°C), and medium pH (7.0), the total alcohols production was almost equal in anaerobic shake flasks and 2-L bioreactor. This essentially means that at optimum process parameters, the scale of operation does not affect the output of the process. The immobilized cells could be reused for multiple cycles for both pure and crude glycerol fermentation.

Improved n-butanol production by a non-acetone producing Clostridium pasteurianum DSMZ 525 in mixed substrate fermentation

“…Despite the high potential of C. pasteurianum for the production of n -butanol (Biebl 2001; Malaviya et al 2012; Khanna et al 2013a, b), only a few publications have dealt with the optimization of n -butanol production with this microorganism. Previously, with C. pasteurianum , instability and great variation in the formation of the two major products 1,3-PDO and butanol was revealed after growth on glycerol (Biebl 2001).…”

“…The author showed that under almost the same conditions, the strain could produce 1.3-PDO or n -butanol as the major product. Recently, many authors have optimized the cultivation conditions to favour the production of one of these two products (Moon et al 2011; Khanna et al 2013a, b). Obviously, both products are essential for the balance of the redox within the cell.…”

“…2). Since pH is known to be a crucial factor affecting the performance of ABE fermentation by Clostridia (Dabrock et al 1992; Haus et al 2011; Moon et al 2011; Malaviya et al 2012; Khanna et al 2013a; Millat et al 2013), the variation of pH in anaerobic bottles may explain such difference. In the anaerobic bottle experiments shown in Fig.…”

“…A weak pathway regulation and the existence of multiplicity have been assumed by Biebl (2001). Recently, Moon et al (2011) and Khanna et al (2013a) optimized the medium compositions to favour n -butanol or 1,3-PDO production in free and immobilized cultures of C. pasteurianum , respectively. Kao et al (2012) studied the co-fermentation of glucose and glycerol by using the strain C. pasteurianum CH4.…”

Impact of butyric acid on butanol formation by Clostridium pasteurianum

“…Although pH values lower than 4.82 would be optimal for butyric acid uptake, there has to be a compromise between optimal growth conditions of C. pasteurianum, formation of butanol and uptake of butyric acid. Cultivation of C. pasteurianum has been reported in a wide pH range between 5 and 7.5, often in a buffered, yet not controlled pH environment (Jensen et al, 2012b;Khanna et al, 2013a;Moon et al, 2011). The degree of butyric acid accumulation is variable in the literature and not fully understood.…”