不同含水量和温度下贮存中球孢白僵菌分生孢子活力与内贮营养的衰变

将球孢白僵菌(Beauveriabassiana)BBSG8702的未干燥孢子粉(含水量58.9±1.6%)和真空冷冻干燥孢子粉(含水量7.4±0.9%)置于4℃和20℃下贮存1个月,每隔5d取样测定活孢率和孢子内贮总糖和蛋白含量,发现含水量和贮存温度交互影响孢子的活力以及内贮总糖和蛋白质的代谢水平,各组合中的活孢率一般与内贮总糖和蛋白质代谢水平均存在显著或极显著相关性.在1个月的贮存期间,4℃下冻干粉总糖含量下降13.4%,蛋白质含量下降39.2%,清水中的萌发率下降32.0%,营养液中的萌发率仅下降6.7%,而未干燥孢子粉的相同指标分别下降42.4%、66.3%、96.4%和99%;在20℃下,冻干粉的上述指标分别下降了14.1%、38.2%、55.8%和 10.4%,而未干燥孢子粉则分别下降了 43.2%、65.4%、99.4%和98.4%. 显然,含水量影响活孢率和内贮营养衰变的幅度,而温度影响衰变的速度,但内贮营养的耗尽并不立即引起孢子失活,在供给外源营养之后孢子仍能萌发.将含水量降至4.0±0.9%的冻干粉贮存1年,4℃下活孢率由初始的99.0%下降至90.2%,而20℃下贮存的前165d活孢率下降较为缓慢,但此后急剧下降,至第240d时几乎全部失活.模拟分析表明,低含水量冻干粉在4℃和20℃下贮存的半衰期(即活孢率减少一半所需的时间)分别为1006d和197d.这些结果说明,白僵菌纯孢粉的含水量

Variation in the viability and the metabolism of internally reserved nutrients of Beauveria bassiana conidia during storage at different regimes of water content and temperature

While the fresh powder (with water content of 58.9 +/- 1.6%) and vacuum-freeze dried (VFD) one (with water content of 7.4 +/- 0.9%) of Beauveria bassiana SGBB8702 conidia were stored at 4 degrees C and 20 degrees C, their viability and contents of internally reserved saccharides and proteins were examined at 5 days intervals. It was found during one-month storage that the water content and temperature interactively affected the levels of conidia viability and the contents of the reserved saccharides and proteins, which in turn correlated considerably well to the viability. Stored at 4 degrees C and 20 degrees C, the VFD conidia lost content of saccharides by 13.4% and 14.1%, content of proteins by 39.2% and 38.2%, and viability by 32.0% and 55.8% when germinating in water only and 6.7% and 10.4% when germinating in 2% glucose solution plus 0.5% peptone, respectively. In contrast, the four estimates of the fresh conidia stored at 4 degrees C and 20 degrees C decreased by 42.4% and 43.2%, 66.3% and 65.4%, 96.4% and 99.4%, and 9.9% and 98.4%, respectively. Thus, water content of B. bassiana conidia affected variation ranges of the viability and the internally reserved nutrients whereas storage temperature influenced their variation rates. However, depletion of the internally reserved nutrients did not necessarily inactivate the conidia. Instead, such conidia may germinate at relatively high level during a period of time as long as being supplied with sufficient nutrients. In another experiment, the powder of VFD conidia with water content being reduced to 4.0 +/- 0.9% were half-monthly examined for viability during one-year storage. The viability only decreased slightly from 99.0% to 90.2% at 4 degrees C by the end of one year. Stored at 20 degrees C, the viability also declined slowly during the first 165 days but dramatically decreased afterwards with little being detected on day 240. A modeling analysis showed that the time for the VFD conidia to lose 50% viability was 1006 days at 4 degrees C and 197 days at 20 degrees C, respectively. Conclusively, the B. bassiana conidia powder, even though its water content was controlled below 5%, can be safely stored for one year or longer at low temperature only but for no longer than 6 months at ambient temperature.