MAL62 overexpression enhances uridine diphosphoglucose-dependent trehalose synthesis and glycerol metabolism for cryoprotection of baker’s yeast in lean dough

Abstract

Background In Saccharomyces cerevisiae, alpha-glucosidase (maltase) is a key enzyme in maltose metabolism. In addition, the overexpression of the alpha-glucosidase-encoding gene MAL62 has been shown to increase the freezing tolerance of yeast in lean dough. However, its cryoprotection mechanism is still not clear. Results RNA sequencing (RNA-seq) revealed that MAL62 overexpression increased uridine diphosphoglucose (UDPG)-dependent trehalose synthesis. The changes in transcript abundance were confirmed by quantitative reverse transcription–polymerase chain reaction (qRT-PCR) and enzyme activity assays. When the UDPG-dependent trehalose synthase activity was abolished, MAL62 overexpression failed to promote the synthesis of intracellular trehalose. Moreover, in strains lacking trehalose synthesis, the cell viability in the late phase of prefermentation freezing coupled with MAL62 overexpression was slightly reduced, which can be explained by the increase in the intracellular glycerol concentration. This result was consistent with the elevated transcription of glycerol synthesis pathway members. Conclusions The increased freezing tolerance by MAL62 overexpression is mainly achieved by the increased trehalose content via the UDPG-dependent pathway, and glycerol also plays an important role. These findings shed new light on the mechanism of yeast response to freezing in lean bread dough and can help to improve industrial yeast strains.

Study of the effect of calcium signal participating in the antioxidant mechanism of yeast under high‐sugar environment

“…This suggested that a high glucose level increased the metabolic output of trehalose, while the addition of Ca 2+ decreased the trehalose output of yeast cells in a high‐glucose environment. Trehalose is a good yeast protector and can protect yeast cells when under stress 46 . Increased yeast trehalose content promotes the normal metabolic functioning of the yeast itself in a high‐glucose environment 29 .…”

“…Trehalose is a good yeast protector and can protect yeast cells when under stress. 46 Increased yeast trehalose content promotes the normal metabolic functioning of the yeast itself in a high-glucose environment. 29 However, the addition of Ca 2+ may protect the activity of yeast through various antioxidant means, so that yeast has a reduced dependence on trehalose metabolism similar to that in the high glucose with Ca 2+ group for intracellular glycerol.…”

Response mechanism of overexpress LBA0625 in Lactococcus lactis NZ9000 at freeze-drying process revealed by transcriptomic analysis

“…The existing dates showed that genetic engineering is a potential method to improve the survival rate of bacteria during freeze-drying. As UGPase plays a highly critical role in cellular integrity, it has been overexpressed in yeast [9] , Dendrobium officinal [10] , Aureobasidium pullulans [2] , and successfully enhanced their freeze-drying tolerance. However, there is little known about the correlation between UGPase with freeze-drying tolerance of LAB.…”