胶质芽孢杆菌(Bacillus mucilaginosus)复合抗热保护剂优化研究

Thermal Protection of Encapsulated Bacillus mucilaginosus

【目的】针对胶质芽孢杆菌(Bacillus mucilaginosus)直投式菌剂菌体存活率低及易失活等问题,对喷雾干燥复合抗热保护剂进行优化研究,以期为其菌剂生产提供理论与技术支持。【方法】以直投式菌剂菌体存活率为指标,利用喷雾干燥生产工艺,考察海藻糖、脱脂奶粉、麦饭石改性材料(H-MS)对菌体的抗热保护效果;并利用响应面法对复合抗热保护剂配方进行优化。【结果】不添加抗热保护剂的菌剂菌体存活率仅有(34.15±1.07)%;添加单一保护剂时,以海藻糖保护效果最佳,麦饭石改性材料(H-MS)及脱脂奶粉次之,菌体存活率分别可达(52.17±1.08)%,(51.64±0.77)%,(43.67±1.62)%,海藻糖和H-MS对菌体存活率具有极显著影响(P<0.01),脱脂奶粉对菌体存活率具有显著影响(P<0.05)。利用响应面优化得到最佳复合抗热保护剂配方为海藻糖4.33%、脱脂奶粉2.90%和麦饭石改性材料(H-MS)7.57%。在此最佳添加配比下,菌体存活率为(73.32±0.76)%,活菌数最高可达1.12×10^(9)CFU·g^(-1)。【结论】添加3种抗热保护剂均能提高直投式菌剂菌体存活率,且三者之间存在交互作用,复合使用的抗热效果优于单独使用。扫描电镜观察显示海藻糖和脱脂奶粉将菌体包埋成微胶囊固定在麦饭石改性材料(H-MS)的孔道中,能有效保护菌体细胞,提高菌剂菌体存活率。

【Objective】Effect of encapsulation to protect Bacillus mucilaginosus from thermal shock was evaluated for formulation optimization.【Method】Rates of survival and activation of B.mucilaginosus encapsulated with trehalose,skimmed milk powder,and/or modified H-MS medical stone after spray-drying were determined.Optimal formulation for the encapsulation was obtained using the response surface method.【Result】The survival rate of the naked B.mucilaginosus was(34.15±1.07)%.In contrast,the encapsulation with trehalose significantly improved the rate to(52.17±1.08)%(P<0.01),while with H-MS,(51.64±0.77)%(P<0.01)and with skimmed milk powder,(43.67±1.62)%(P<0.05).Furthermore,a combined use of trehalose at 4.33%,skimmed milk powder at 2.90%,and H-MS at 7.57%for the encapsulation,the survival reached(73.32±0.76)%with a microbial count of 1.12×10^(9) CFU·g^(-1).【Conclusion】The three encapsulation materials,especially,when they were applied in combination,significantly raised the B.mucilaginosus survival rate under a heat treatment.The scanning electron microscopic image revealed that trehalose and skimmed milk powder immobilized the bacteria cells in H-MS pores producing an effective thermal insulation that sheltered the encapsulated microbes.