Thermotolerant Zymomonas mobilis: Comparison of Ethanol Fermentation Capability with that of an Efficient Type Strain

Abstract

Abstract:Zymomonas mobilis is an alternative microorganism to Saccharomyces cerevisiae for ethanol production. To find a thermotolerant Z. mobilis strain, the growth and ethanol production of four isolates in Thailand were compared with those of the efficient strain ZM4 (NRRL B-14023) at different temperatures. One of the selected strains, TISTR 405, was found to grow and produce ethanol even at 39˚C to an extent similar to that at 30˚C, and the growth and ethanol productivity at 39˚C were better than those of ZM4 at 30˚C, suggesting that TISTR 405 is suitable for ethanol fermentation at high temperatures. Analysis of genes directly related to ethanol formation or degradation, adhA, adhB and pdc, encoding alcohol dehydrogenase (Adh) A, AdhB and pyruvate decarboxylase, respectively, revealed that these genes were highly conserved in both strains. Comparison of their gene expression and activity of the products in both TISTR 405 and ZM4 at different temperatures or growth phases indicated that there was not a great difference at the transcriptional level, but the total activity of AdhA and AdhB in TISTR 405 was higher than that in ZM4. Both strains showed a significant increase in AdhB activity in the stationary phase.

The Crucial Role of Alcohol Dehydrogenase Adh3 inKluyveromyces marxianusMitochondrial Metabolism

“…RT-PCR analysis was performed as described previously. 4,17) The primers used for KmNDI1, KmNDE1, KmGUT2, and KmACT1 were KmNDI1-5:…”

Thermotolerant genes essential for survival at a critical high temperature in thermotolerant ethanologenic Zymomonas mobilis TISTR 548

“…Moreover, it is assumed that these genes are involved in the response of cells to other stresses including osmotic stress or oxygen stress. In fact, Z. mobilis increases thermotolerance by the addition of sorbitol [ 72 ] and exhibits faster growth and higher ethanol production under a static condition than that under a shaking condition [ 19 , unpublished]. Further experiments are required for clarifying this assumption.…”

“…Zymomonas mobilis TISTR 548 [ 19 , 20 ] and its derivatives were grown in YPD (3% glucose, 0.5% peptone, and 0.3% yeast extract) medium. E. coli S17-1 harboring pSUP2021 Tn 10 [ 30 ] was grown in LB (0.5% yeast extract, 1% NaCl, and 1% Bactotryptone) medium supplemented with 12.5 µg/ml of tetracycline.…”

“…Thus, thermotolerant Z. mobilis is thought to be beneficial for the production of useful materials. Z. mobilis TISTR 548 is a thermotolerant strain that can grow even at 39 °C [ 19 – 21 ], which is 5–10 °C higher than the optimum temperature for the same genus [ 22 ] and the same species [ 1 , 23 ], and it can efficiently produce ethanol to an extent similar to that of ZM4 [ 3 ]. However, information on the molecular mechanism of the thermotolerance of thermotolerant Z. mobilis is limited, though some heat shock proteins have been analyzed [ 24 , 25 ].…”

“…E. coli is intrinsically thermotolerant compared to general mesophilic microbes and used for production of useful materials like amino acids, hormones, or vaccines. Z. mobilis TISTR548 and A. tropicalis are thermotolerant and efficiently produces ethanol and acetic acid, respectively, at relatively high temperatures [ 19 , 29 ]. Thus, the knowledge of the general strategy might be applicable for relatively thermosensitive mesophilic microbes that have been utilized for production of useful materials in fermentation companies.…”