Influence of high osmotic pressure on sorbitol production by Zymomonas mobilis

Abstract

The objective of the present work was to study the variation on the sorbitol production in relation to the concentration of sugars, (metabolizable or not) and the cultivation time. A full factorial design was used considering the factors such as sucrose and maltose concentration and cultivation time. The addition of sugars caused increases on the sorbitol production up to the concentration of 300g/L however, decreases on the sorbitol production were observed when the concentration reached values above this.Increasing the time of fermentation was statistically significant to sorbitol production, however, little increase the production was noticed after 36h.

Sorbitol production from mixtures of molasses and sugarcane bagasse hydrolysate using the thermally adapted Zymomonas mobilis ZM AD41

“…Reducing sorbitol content at high sugar concentrations might be due to excessive osmotic pressure that negatively affects cell growth and metabolism. It is noteworthy that the results obtained in this study differed from those reported by Cazetta et al 43 , de Barros and Celligoi 10 , and Vignoli et al 20 , who demonstrated that a sugar concentration of 300 g/L favored the formation of sorbitol by Z. mobilis strain ATCC 29,191. This finding suggested that different strains of Z. mobilis respond to different sugar concentrations for sorbitol production.…”

“…The maximum sorbitol concentration produced by a thermally adapted Z. mobilis ZM AD41 using SM (31.23 g/L) or a mixture of SM and SBH (30.45 g/L) at a sugar concentration of 200 g/L was greater than that of Chamnipa et al 16 , who reported a maximum sorbitol content of 5.89 g/L by Z. mobilis TISTR548 using a mixture of SBH and cassava pulp hydrolysate (CPH) as feedstock. In addition, the sorbitol content in the current study was also comparable to those of Vignoli et al 11 and Vignoli et al 20 , using sucrose or a mixture of sucrose and maltose as feedstock. Notably, a high sorbitol concentration (161.10 g/L) was also recorded by recombinant Z. mobilis overexpressing the glo gene using a mixture of glucose and fructose as raw material at a sugar concentration of 300 g/L 12 .…”

“…It also forms and accumulates in a medium comprising glucose and fructose 38 , 39 . Previous studies demonstrated that sorbitol is primarily produced under high concentrations of sugar, specifically high sucrose concentrations, which favor the accumulation of fructose 20 , 40 . Since sorbitol is classified as a microbial osmoprotectant, the accumulation of sorbitol could protect microbial cells against the dehydration effects of high external osmolarity 41 .…”

“…Zymomonas mobilis , a Gram-negative facultative anaerobic bacterium, is among the most promising sorbitol-producing microorganisms since it possesses several ideal industrial biocatalyst properties, such as low biomass yield, low oxygen requirements, high osmolarity tolerance, high ethanol tolerance, high sugar uptake and conversion rate, and high product formation rate 17 . Several strains of Z. mobilis have been investigated for their sorbitol production efficiency, such as Z. mobilis 113S 18 , CP4 9 , ZM4 (ATCC 31,821) 19 , ATCC 29,191 10 , 11 , 20 , pHW20a- gfo 12 , and TISTR548 16 . Most of these strains, except strain TISTR548, could grow and produce high sorbitol concentrations at a normal growth temperature (30 °C).…”

Lowering whole cost for sugarcane‐based ethanol production by engineered Zymomonas mobilis

“…However, previous study has shown that interference with the gfo gene in Z. mobilis resulting in poor growth and reduced ethanol fermentation capacity (Sootsuwan et al, 2013), likely because sorbitol serves as an osmoprotectant to counteract the inhibitory effects of high sugar or other products (e.g., ethanol, organic acid, etc.) on Z. mobilis (Vignoli et al, 2010). So far, there is no report on the enhancement of ethanol production by reducing levan metabolism.…”