耐高温二羧酸突变株HYU_m的研究

STUDIES ON THERMOTOLERANT DIOIC ACIDS PRODUCING MUTANT HYU_m

用HNO_2及紫外线在38℃高温下直接诱变和筛选野生菌株热带假丝酵母(Candida tropi-calis)1045,得到一株在高温下能利用C_(10)(?)C_(18)单一正烷烃产生与基质链长相应的单一二羧酸的耐高温突变株HYU_m。该突变株的最高生长温度为40℃,最适产酸温度为32～36℃,高于或低于此温度范围产酸量大多下降。高温能提高诱变剂对诱变细胞的杀伤力,以及加大诱变后存活细胞的死亡率.高温直接诱变1045菌株获得耐高温产酸突变株要比从已丧失高温产酸突变株U_(3-21)中筛选耐高温株的几率高得多。突变株HYU_m 的耐高温性能是从亲本株直接保留下来,并可以通过传代稳定地遗传下去.突变株HYU_m 利用C_(10)(?)C_(18)正烷烃表现出明显的基质特异性,除DC_(11)外。奇数二羧酸DC_(13)、DC_(15)、DC_(17)的产量都很高。流加可大幅度增加产酸最,产酸量及产酸速度与种子浓度及摇床速度关系密切.HYU_m 突变株在Bioflo-Ⅱ型发酵罐上的DC_(13)产量为109g/L.

Treatment and cultivation of wild strain,Candida tropicalis 1045,with nitrous acid and ultraviolet rays at high temperature(38℃)resulted in a ther- motolerant mutant HYU_m which could produce a large amount of DC_(10)～DC_(?) from n-C_(10)～C_(?) at high temperature after fermenting for 96-144h.This ther- motolerant mutant HYU_m could grow at 40℃ while the range of optimum temperature for dioic acid prodution was 32～36℃.The yields of dioic acids de- creased when the temperature was below 32℃ or over 36℃. Mutagen promoted the lethality of cells 1045 at high temperature and also killed most of the survivors treated with HNO_2 and ultraviolet ray.The mu- tation rate of thermotolerant mutant directly obtained at high temperature is much higher than that of the probability(3×10^(-8))by selection from mutant U_(3-21) which could not grow and produce dioic acids at high temperature.The thermotolerant property of mutant HYU_m was kept from its parant strain 1045 and maintained stable by subcultures. Thermotolerant mutant HYU_m could produce and accumulate a series of DC_(10)～DC_(?) and DC_m from corresponding chain length of n-alkanes(C_(10)～C_(?))and n-alkane mixture(C_m) but showed obvious substrate specificity.The dioic acid of highest yield was DC_(13) followed by DC_(17) and DC_(15).Yields of DC_(16) and DC_(18) were the lowest.Therefore,mutant HYU_m looks like a good producer for odd dioic acids except DC_(11).The yields and rate of dioic acids production by mutant HYU_m were associated with the density of seeds and the speed of shaker.In the course of fermentaion substrate supplementation could increase the pro- duction of dioic acids.The yield of DC_(13) in 6.6 liter Bioflo-Ⅱ jar is 82.7g/L at high temperature(36℃).