产多糖溶磷细菌对难溶性Ca-P的活化特性

Characteristics of insoluble calcium phosphate activated by phosphate solubilizing bacteria producing exopolysaccharide

以肠杆菌EnHy-401、节杆菌ArHy-505、固氮菌AzHy-510和巨大芽孢杆菌P17为材料,比较了4种溶磷细菌在摇瓶培养条件下对不同难溶性Ca-P中的磷活化能力。结果表明,4种溶磷细菌均能促使难溶性Ca-P中的磷活化,但3种产多糖的溶磷细菌(EnHy-401、ArHy-505、AzHy-510)对难溶性Ca-P的活化能力普遍强于不产多糖的溶磷细菌(P17),肠杆菌EnHy-401对Ca3-P、Ca8-P和Ca10-P中的磷活化率分别达61.53%、63.40%和4.32%。在产多糖的溶磷细菌中,有机酸和多糖均高的菌株活化磷的能力最高,3种产多糖的溶磷细菌活化难溶磷酸钙能力的大小顺序依次为肠杆菌EnHy-401、节杆菌ArHy-505、固氮菌AzHy-510。结果还表明,产多糖的溶磷细菌对难溶磷的活化作用是由分泌有机酸和多糖的协同作用实现的,多糖对磷的吸持推动了磷的溶解平衡向溶解方向移动,且该协同作用受胞外多糖持磷能力和环境中C/N的影响,单位体积发酵液中多糖持磷量与菌株的磷活化能力呈正相关。在本试验条件下,C/N值高时,多糖产量高,有机酸分泌多,活化磷的能力就强。同一菌株只有在最适于产有机酸和产多糖的C/N值下,才能表现出最佳的溶磷效果。

The capacities of phosphate solubilizing bacteria （PSB） which was Enterobacter sp. EnHy-401, Arthrobacter sp. ArHy- 505, Azotobacter sp. AzHy-510 and Bacillus megaterium P17 to activate insoluble calcium phosphates were investigated, respectively. It was found that all tested strains could activate poorly soluble calcium phosphate well, but PSB （EnHy-401, ArHy-505 and AzHy-510） producing exopolysaccharide （EPS） had higher ability of phosphate solubilization than PSB isolate P17 without producing EPS. 61.53, 63.40 and 4. 32 percent of the phosphorus were released from Ca3-P, Cas-P and Cal0-P by EnHy-401, respectively. There were also significant differences among the PSB isolates producing EPS, the strain with higher ability of producing organic acid and EPS showed stronger ability compared with that isolates producing lower organic acid and EPS to dissolve insoluble calcium phosphates, and PSB EnHy-401 showed the maximum solubilization in Ca-P, followed by ArHy-505 and AzHy-510. Further studies showed that EPS might be another factor in the microbial dissolution of tricalcium phosphate except for organic acid, and the increase of P-solubilization brought by EPS attributed to the participation of EPS led to the change in homeostasis of P-solubilization, pushing it towards P dissolved by holding free phosphorus in the medium, consequently resulting in greater phosphorus released from insoluble phosphate. The synergistic effects of EPS and organic acid on Ca-P solubilization were also affected by C/N in the medium. In general, the higher C/N, the more quantity of organic acid and EPS would be produced, and the higher phos- phorus contents would be activated. These strains showed strongest ability to dissolute phosphates when supplied fitter C/N for organic acid and EPS production in the medium.