Effect of cultivation mode on a bioprocess for chromium yeast biomass enrichment
Effect of cultivation mode on a bioprocess for chromium yeast biomass enrichment
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DOI：
10.1007/s004240000096
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发表时间：
2000-01-01
影响因子：
4.5
通讯作者：
Raspor, P
中科院分区：
文献类型：
--
作者：
Batic, M;Raspor, P
确定的酵母菌生长培养基含278.8 mM葡萄糖和0.1 mM铬(III)，以K2Cr(SO4)(2)形式添加。采用12H2O间歇培养和间歇/补料组合培养模式。在补料分批培养模式下，酵母菌生长过程中底物添加速率保持不变，对应的生长速率为0.25h(-1)。在这两种情况下，通过在线测量30℃下的光密度、pH和Po(2)来跟踪酵母的生长和活性。在生物过程结束时，通过缩二脲反应离线测定酵母生物量中的蛋白质浓度。用ETA-AAS法测定总铬和有机结合铬。不同培养方式对添加铬的酵母菌细胞总蛋白浓度有影响。间歇发酵的蛋白质含量占干酵母生物量的25.7%，而同期混合发酵的蛋白质含量为16.9%。栽培方式对铬吸收的影响表现在总铬积累量上，总铬积累量达8.68+/-0.16mmolg(-1)d.wt。分批培养和分批/补料分批联合培养的干酵母生物量为1.92+/-0.04 mU·g~(-1)。有机结合铬的情况正好相反。在酵母分批/补料组合生长过程中，60%的铬是有机结合的。酵母分批培养时，这一数值达到13.5%。结果表明，无论酵母生物量中蛋白质的比例如何，分批/补料分批相结合的培养模式比分批培养模式更能有效地将铬转化为有机结合铬。
Defined cultivation media for yeast growth which contained 278.8 mM of glucose and 0.1 mM of chromium(III) added as K2Cr(SO4)(2). 12 H2O was used in batch and combined batch/fed-batch cultivation mode. In fed batch cultivation mode the rate of substrate addition remained constant during growth of yeast and corresponded to a growth rate of 0.25 h(-1). In both cases the growth and yeast activity was followed by on line measurement of optical density, pH and pO(2) at 30 degrees C. At the end of the bioprocess the concentration of protein in yeast biomass was determined off line by the biuret reaction. Total and organically bound chromium was detected by ETA-AAS. Different cultivation modes affected the total cell protein concentration of yeast grown in media supplemented with chromium. In batch process the protein content represented 25.7% of dry yeast biomass, in contrast in the mixed bioprocess this value was 16.9% one the same period of time. The influence of cultivation mode on chromium uptake was seen in total chromium accumulation which reached 8.68 +/- 0.16 mu mol g(-1) d.wt. in batch and 1.92 +/- 0.04 mu mol of chromium g(-1) of dry yeast biomass in combined batch/fed-batch cultivation mode. The opposite was observed for organically bound chromium. The 60 % of total accumulated chromium was organically bound during yeast growth in combined batch/fed-batch mode. When yeast was grown in batch mode this value attained 13.5 %. Results suggested that a combined batch/fed-batch mode of cultivation was more effective over a batch system in chromium biotransformation to organically bound chromium, regardless of the lower protein ratio determined in the yeast biomass.