Abstract:The effect of sodium fluoride on the determination of acid trehalase activity in baker’s yeast was investigated in this study. The recombinant baker’s yeast stains TL-105(hxt14?) and TL-106(gal2?) with deleted genes encoding the hexose transporters were constructed. The acid trehalase activity, the secretion of neutral trehalase and acid trehalase, the secretion of glucose and trehalose and the uptake of extracellular glucose of BY6-9α (parental strain), TL-103(ath1?), TL-104(agt1?), TL-105(hxt14?) and TL-106(gal2?) were measured. It was found that sodium fluoride had less effect on the secretion of neutral trehalase, acid trehalase and trehalose, although it had obvious effect on the assay of acid trehalase activity. Thus, sodium fluoride was not related to the secretion of intracellular trehalase or trehalose in the assay of acid trehalase activity. The acid trehalase activity, examined by citrate procedure, of strains TL-105(hxt14?) and TL-106(gal2?) at the stationary phase was 17.06% and 300.23% higher than those of the parental strain, respectively. However, the acid trehalase activities of the three strains examined by citrate and sodium fluoride method showed less difference. Furthermore, the extracellular glucose concentration of strains BY6-9α and TL-103(ath1?) at the exponential phase, which was incubated at 30 ℃ for 30 min with sodium fluoride before the acid trehalase activity was assayed, was 108.53±1.39 and 30.53±1.02 mg/L in the reaction mixture, respectively. These results indicated that sodium fluoride significantly affected the uptake of extracellular glucose and led to the secretion of intracellular glucose. Hence, the acid trehalase activity of the strains treated with sodium fluoride was higher than those without sodium fluoride treatment.
