【作者】 周学永；

【导师】 喻子牛； 黄巧云；

【作者基本信息】 华中农业大学 ， 微生物学， 2004， 博士

【摘要】 系统研究了喷雾干燥塔进风口温度、出风口温度和喷头压力对苏云金芽胞杆菌芽胞和伴胞晶体含量的影响。芽胞和伴胞晶体含量均随干燥温度升高而降低，但二者对温度的敏感程度不同，进风口温度引起芽胞和晶体失活的拟Z值参数分别为250℃和740℃；出风口温度引起芽胞和晶体失活的拟Z值参数分别为72.7℃和270℃。根据出风口温度计算的结果，芽胞热失活活化能为112.24 kJ·mol^-1，晶体热失活活化能为123.88 kJ·mol^-1。喷头压力在0.10～0.25 MPa之间变化时，对芽胞和晶体含量的影响不显著，填料对芽胞和晶体具有一定的热保护作用。 通过正交试验确定了苏云金芽胞杆菌发酵液喷雾干燥过程中影响原粉收率、含水量、晶体蛋白含量、芽胞数和杀虫致死率的主要因素。方差分析表明，对产品收率的影响顺序为：喷头压力＞进风口温度＞进料速度；对含水量、晶体蛋白含量、芽胞数和杀虫致死率的影响顺序为：进风口温度＞进料速度＞喷头压力。建立了描述喷雾干燥工艺参数与产率、含水量、晶体蛋白含量、芽胞数和杀虫致死率之间关系的数学模型，该模型可以直观地发映出工艺操作参数对上述指标的影响趋势，调整这些工艺参数就可以达到控制产品性能的目的。根据数学模型确定的最佳操作条件为：进风口温度180℃，进料速度60 ml min^-1，喷头压力0.1 MPa。验证试验证实，所建立的数学模型具有可靠性。相关研究国内外未见公开报道。 研究了离心和微滤浓缩处理对苏云金芽胞杆菌发酵液芽胞数、晶体含量、效价和流变特性的影响。经离心和微滤浓缩处理后，发酵液密度、粘度和含固量增加，芽胞数、晶体含量和效价提高，但效价收率一般随浓缩倍数的增加而降低。上清液或浓缩上清液补加到浓缩发酵液中可以提高效价收率，就浓缩方法而言，微滤浓缩比离心浓缩更能保持浓缩发酵液的杀虫活性。浓缩发酵液喷雾干燥后，原粉的效价、晶体含量和芽胞数提高，但浓缩倍数超过2.5倍时，效价收率随浓缩倍数的增加而降低。发酵液加填料直接喷雾干燥可以保持较高的效价收率，是最大程度回收杀虫活性成分的有效办法。 苏云金芽胞杆菌发酵液中添加0.5％～1.0％（w／v）的适宜填料可以提高喷雾干燥产率，但当填料用量达到3％以上时，产品收率一般呈下降趋势。相关性分析表明，填料的松密度和振实密度与喷雾干燥产率呈高度负相关关系，即密度越大，产率越低；对同一种填料而言，颗粒越细，产率越高。填料的休止角与喷雾干燥产率低度相关。上述规律的发现对专业工厂筛选高效填料具有指导意义。 国内率先研究了68 kDa和130 kDa杀虫蛋白在纳米级土壤和矿物胶体上的吸附特性、解吸特性和杀虫活性。供试胶体在pH 9.0碳酸盐缓冲体系对苏云金芽胞杆菌68 kDa和130 kDa杀虫蛋白的等温吸附曲线均符合langmuir方程（R²＞0.97），对68扔a杀虫蛋白饱和吸附量的高低顺序依次为:蒙脱土>红壤胶体>针铁矿>高岭土>氧化锌>氧化硅;对130 kDa杀虫蛋白饱和吸附量的高低顺序依次为:蒙脱土>氧化锌>红壤胶体>氧化硅>高岭土>针铁矿。供试胶体在磷酸盐体系pH6一7的吸附量最高，在碳酸盐体系的吸附量随pH值升高而降低。与碳酸盐相比，磷酸盐具有抑制针铁矿、蒙脱土、氧化锌和红壤胶体吸附杀虫蛋白的作用。 杀虫蛋白很容易被供试胶体吸附，0.5一3h就能达到或接近最饱和吸附量。随着杀虫蛋白与胶体质量比例增加，胶体对杀虫蛋白的吸附量增加，而吸附百分率降低。1。一50℃内，温度对供试胶体吸附杀虫蛋白的影响不大。透射电镜分析表明，本研究所使用的土壤矿物胶体水中分散粒径在100 nm以下，吸附杀虫蛋白后粒径没有明显变化，仍属于纳米颗粒范畴。X-射线衍射分析显示，蒙脱土吸附杀虫蛋白后没有引起片层间距扩张。红外光谱分析证实，吸附的杀虫蛋白己结合在胶体上。 纯化毒素与供试胶体吸附的毒素对棉铃虫幼虫均具有杀虫活性，且后者的LC50低于前者。紫外光降解试验表明，蒙脱土和红壤胶体具有减轻紫外光对杀虫蛋白的降解作用，氧化锌和高岭土则起加速降解的作用。胶体一杀虫蛋白复合物冷冻干燥和喷雾干燥后，杀虫活性有较大程度下降。 被蒙脱土、红壤胶体、氧化硅、氧化锌、针铁矿和高岭土吸附的68 kDa杀虫蛋白经去离子水三次洗涤后，总解吸率分别为28.55%、32.38%、40.54%、24.66%、24.72%和31.10%;pHg碳酸盐缓冲液三次洗涤后的总解吸率相应为21.69%、18·43%·38·81%、15.37%、16.34%和24.64%，解吸能力低于去离子水。被上述胶体吸附的130 kDa杀虫蛋白去离子水三次解吸率为17.79卜64.90%，pHg碳酸盐缓冲液三次解吸率为16.61卜59.05%。更多还原

【Abstract】 The effects of inlet air temperature, outlet air temperature and atomizing air pressure on the spores and crystal protein content of Bacillus thuringiensis were studied. The spores and crystal protein content decreased with the drying temperature and their sensitivity to the temperature was different. The pseudo-z value ( a temperature increase needed for one log cycle reduction) of spores and crystal protein content caused by inlet air temperature was 250C and 740C respectively; the pseudo-z value of spores and crystal protein content caused by outlet air temperature was 72.7C and 270 C respectively. The activation energy of spore and crystal protein calculated by the outlet air temperature was 112.24 kJ mol-1 and 123.88 kJ mol-1 respectively. No obvious changes were found for the spores and crystal protein content as the atomizing air pressure increased from 0.10 MPa to 0.25 MPa. The filler gave some protection to the spores and crystal protein from heat.The effects of inlet air temperature, liquid feed rate and atomizing air pressure on the yield, moisture content, crystal protein content, spores and lethality of Bacillus thuringiensis powder during the spray drying of Bacillus thuringiensis fermentation liquor were studied by an orthogonal experiment. The results of variance analysis indicated that the extent of influence of factors on the yield of Bacillus thuringiensis was in the order: atomizing air pressure> inlet air temperature> liquid feed rate; and on the moisture content, crystal protein content, spores and lethality of Bacillus thuringiensis was in the order: inlet air temperature> liquid feed rate> atomizing air pressure. The mathematical models describing the relationship between spray drying parameters and the yield, moisture content, crystal protein content, spores and lethality of Bacillus thuringiensis were established. The influential trends of operation parameters to the product properties could be shown directly by these models, and the performance of the production could be controlled by adjusting these parameters. The optimum spray drying conditions determined by these mathematical models were: inlet temperature 180C, liquid feed rate 60 ml min", atomizing air pressure 0.1 MPa. The results of the validation experiment showed that these mathematical models established by the orthogonal experiment were reliable. Available data showed that this important post-treatment technology was seldom reported up to now.The effects of centrifugation and micro-filtration concentration of the fermentationliquor on the spores, crystal protein content, titer and rheological properties were studied. After concentration of the fermentation liquor, the density, viscosity, solid content, spores, crystal protein content and titer increased, but the titer yield decreased. The addition of supernatant or concentrated supernatant to the concentrated fermentation liquor leaded to the increase of the titer yield. By comparison of both concentration methods, the micro-filtration concentration was more favorable for increasing the titer yield of the concentrated fermentation liquor than the centrifugation concentration. The titer, spores and crystal protein content of spray dried powder of concentrated fermentation liquor were higher than those of spray dried powder of fermentation liquor without concentration, but the titer yield decreased if the concentration times was more than 2.5. The spray drying of fermentation liquor added by filler without concentration was a effective method for recovering bioactive components.The yield of spray dried powder increased if .the fermentation liquor added by 0.5%~1.0%(w/v) filler, however, the yield of spray dried powder decreased as the filler content was more than 3.0%(w/v). The results of correlation analysis showed that there was a highly negative correlation between the density of filler and spray drying yield, the higher the density, the lower the yield; as far as the same filler was concerned, the finer the particle size, the higher the yield. The above laws can give更多还原