Abstract
The effect of the variables pantothenic acid, yeast extract and sodium chloride, as well as the cell permeabilization technique, were investigated on the formation of levan, ethanol, sorbitol and biomass of Zymomonas mobilis, using a 2 4-1 fraction factorial design. Cell growth was determined by turbidimetry at 605 nm, relating it to a biomass with a dry weight calibration curve. Reducing sugars were quantified according to Somogyi and Nelson. Total sugars were quantified by the phenol-sulfuric acid method, sorbitol by HPLC and ethanol. The levan produced was precipitated by the addition of absolute ethanol and quantified in fructose units. In levan biosynthesis, the variable that had the largest contribution was cell condition. The results suggested that the factors that most affected biomass and ethanol formation were sodium chloride concentration and cell condition that affected negatively on production. For sorbitol, the variable that had a significant effect was permeabilization, which decreased its synthesis. Studies to amplify the range of established factors would be important.
Highlights
Zymomonas mobilis is of main commercial interest for producing ethanol as a biofuel
The objective of the present study was to evaluate the effect of cell permeabilization and the addition of nutritional factors in the formation of levan and other bio-products by Zymomonas mobilis
The largest levan biosynthesis was with cell inoculum of 0.8 g L-1
Summary
Zymomonas mobilis is of main commercial interest for producing ethanol as a biofuel. In sucrose medium, it synthesizes several products such as sorbitol, gluconic acid, levan and fructo-oligosaccharide (VIIKARI, 1984). The biosynthesis of such bio-technological products may be affected by the concentration of nutrients in culture medium, by environmental conditions (YOO et al, 2004), and by the new biotechnological processes, cell permeabilization and immobilization (RERH et al, 1991; PARK et al, 1994). The permeabilization process has been a tool used by different authors to improve the production of sorbitol and gluconic acid (SILVEIRA; JONAS, 2002). Jang et al (2001) reported that using toluenepermeabilized whole cells produced low molecular weight levan The permeabilization process has been a tool used by different authors to improve the production of sorbitol and gluconic acid (SILVEIRA; JONAS, 2002). Jang et al (2001) reported that using toluenepermeabilized whole cells produced low molecular weight levan
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