Improved Leavening Ability of a Wild Yeast, <i>Saccharomyces cerevisiae</i> AK46 2-deoxyglucose Resistant Mutant

Abstract

The wild yeast Saccharomyces cerevisiae AK46 was isolated from cherry fruits and commercialized as baker's yeast. We isolated a 2-deoxyglucose (2-DOG)-resistant mutant of AK46 (MCD4) and evaluated its leavening ability in bread dough. Our findings show that the maltose utilization of MCD4 was significantly enhanced in the presence of glucose and α-glucosidase activity was increased by approx. 1.6-fold compared to that of AK46, indicating release from catabolite repression. In addition, baking performance results using the sponge dough and no-time dough methods showed that the CO 2 production rate of MCD4 was increased by approx. 1.6-fold (sponge and dough method) and the specific volume of bread was increased by 6.3% and 7.8%, respectively. These results demonstrate that the 2-DOG resistance exhibited by MCD4 significantly improved the leavening ability in bread dough.

A 2-Deoxyglucose-Resistant Mutant of Saccharomyces cerevisiae Shows Enhanced Maltose Fermentative Ability by the Activation of MAL Genes

“…Saccharomyces cerevisiae MCD4 with 2-DOG-resistance showed a higher ability of maltose fermentation compared with the parent strain AK46 as well as a standard baker’s yeast HP216, which was used as a comparative control [ 15 ]. Therefore, to investigate the relationship between 2-DOG resistance and maltose fermentative ability, a total of 120 haploid isolates of MCD4 were obtained, and their growth abilities in the 2-DOG-containing medium and fermentative abilities (reduction in total weight by the CO 2 production) in maltose-medium were evaluated ( Figure 1 ).…”

“…S. cerevisiae strain AK46 was isolated in a previous study [ 11 ]. The 2-DOG mutant strain derived from AK46—MCD4—was constructed as previously described [ 15 ].…”

“…The fermentative ability in liquid medium was measured as described previously [ 15 ]. Briefly, 5 mL cell suspension including yeast cells (200 mg dry weight) was inoculated into 20 mL maltose-medium (8.0% maltose, 0.3% NaH 2 PO 4 ∙2H 2 O, 0.2% MgSO 4 ∙7H 2 O, 0.08% KCl, 0.002% thiamine, 0.002% pyridoxine, and 0.02% nicotinic acid) in a 100 mL Erlenmeyer flask (HARIO, Tokyo, Japan) and incubated at 30 °C for 3 h aerobically (80 rpm).…”

“…Briefly, yeast cells were incubated in YPD medium at 30 °C for 24 h aerobically and collected by centrifugation at 15,000× g for 10 min at 4 °C. The total DNA was extracted from cells using the ZR Fungal/Bacterial DNA kit (ZYMO Research, Irvine, CA, USA) and sequenced as described in a previous study [ 15 ]. To identify amino acid substitutions/deletions in proteins associated with maltose metabolism and catabolite repression, the Bioedit multiple sequence alignment editor (Ibis Biosciences, Carlsbad, CA, USA), the BLAST database, and Tablet [ 17 ] were used.…”

“…In addition, 2-DOG-resistant mutants having maltose-deregulated phenotype were reported to improve leavening ability in bread dough [ 13 , 14 ]. Thus, we isolated a 2-DOG-resistant mutant derived from AK46 (termed MCD4) and showed its improved leavening ability in bread dough along with increased maltose fermentation, which was caused by a release from catabolite repression [ 15 ]. However, it is not understood how the MCD4 genes associated with the 2-DOG resistance cause the increase of maltose fermentation.…”