Production of Paenibacillus polymyxa biofertilizer using potato starch wastewater for vegetable cultivation
LIU Hao1,2,3,, LI Rui2,3,4, BAO Lijun2,3,4, WANG Fenfen2,3,5, ZHANG Xupo2,3,5, QU Dong1, BAI Zhihui2,3,4,, 1.College of Resource and Environment, Northwest A&F University, Yangling 712100, China 2.State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China 3.Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China 4.College of Environment & Resources, University of Chinese Academy of Sciences, Beijing 100049, China 5.College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China
Abstract:Potato starch wastewater contains high concentration of starch, protein and other organic matter. Using potato starch wastewater to cultivate plant growth-promoting bacteria is a method to realize its resource utilization. The growth conditions of Paenibacillus polymyxa EBL06 strain cultured in potato starch wastewater were optimized using a comibined single-factor and central composite design (CCD) approach, in which three key factors, i.e., wastewater volume fraction (concentration), culture temperature and initial pH, were focused. In this context, the optimum conditions for the culture of P. polymyxa obtained from the experiment were as follows: COD concentration 13.7 g·L?1, initial pH 7.17, culture temperature 31.4 ℃. Under this condition, the number of living bacteria was 6.2×109 cfu·mL?1, which was consistent with the CCD predictions, and satisfying the national standard of agricultural microbial agents (GB 20287-2006). To verify the application effect of the microbial agent, the experiment of vegetable planting was then carried out. The results showed that the P. polymyxa biofertilizer could significantly increase the yield and quality of pakchoi; its fresh weight, dry weight, plant height and vitamin C content increased by 68.6%, 13.7%, 5.6% and 41.3%, respectively; compared with the fertilization of chemical fertilizer only, the mixed fertilization of P. polymyxa biofertilizer and urea fertilizer could improve the nitrogen utilization efficiency, and resulted in an increment in the content of vitamin in pakchoi plant by nearly 25.3%, and meanwhile, contributed to an decrease in the content of nitrate decreased by 15.3%. Overall, this study provides a meaningful reference for the resource utilization of potato starch wastewater, as well as the application and popularization of P. polymyxa. Key words:potato starch wastewater/ Paenibacillus polymyxa/ plant growth-promoting bacteria/ central composite design (CCD)/ biofertilizer.
图1废水含量对P. polymyxa生长的影响 Figure1.Effect of wastewater content on production of P. polymyxa
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1.College of Resource and Environment, Northwest A&F University, Yangling 712100, China 2.State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China 3.Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China 4.College of Environment & Resources, University of Chinese Academy of Sciences, Beijing 100049, China 5.College of Environmental Science and Engineering, Hebei University of Science and Technology, Shijiazhuang 050018, China Received Date: 2020-06-29 Accepted Date: 2020-07-28 Available Online: 2020-09-05 Keywords:potato starch wastewater/ Paenibacillus polymyxa/ plant growth-promoting bacteria/ central composite design (CCD)/ biofertilizer Abstract:Potato starch wastewater contains high concentration of starch, protein and other organic matter. Using potato starch wastewater to cultivate plant growth-promoting bacteria is a method to realize its resource utilization. The growth conditions of Paenibacillus polymyxa EBL06 strain cultured in potato starch wastewater were optimized using a comibined single-factor and central composite design (CCD) approach, in which three key factors, i.e., wastewater volume fraction (concentration), culture temperature and initial pH, were focused. In this context, the optimum conditions for the culture of P. polymyxa obtained from the experiment were as follows: COD concentration 13.7 g·L?1, initial pH 7.17, culture temperature 31.4 ℃. Under this condition, the number of living bacteria was 6.2×109 cfu·mL?1, which was consistent with the CCD predictions, and satisfying the national standard of agricultural microbial agents (GB 20287-2006). To verify the application effect of the microbial agent, the experiment of vegetable planting was then carried out. The results showed that the P. polymyxa biofertilizer could significantly increase the yield and quality of pakchoi; its fresh weight, dry weight, plant height and vitamin C content increased by 68.6%, 13.7%, 5.6% and 41.3%, respectively; compared with the fertilization of chemical fertilizer only, the mixed fertilization of P. polymyxa biofertilizer and urea fertilizer could improve the nitrogen utilization efficiency, and resulted in an increment in the content of vitamin in pakchoi plant by nearly 25.3%, and meanwhile, contributed to an decrease in the content of nitrate decreased by 15.3%. Overall, this study provides a meaningful reference for the resource utilization of potato starch wastewater, as well as the application and popularization of P. polymyxa.
1) P. polymyxa菌剂对蔬菜鲜质量、干质量及株高的影响。P. polymyxa菌剂对蔬菜鲜质量、干质量及株高的影响:图7与图8分别为不同施肥处理对蔬菜质量和株高的影响。各处理组的蔬菜鲜质量明显高于CK。在相同施氮水平下,相比于空白组,P. polymyxa菌剂与尿素减量混施(C+M)处理组蔬菜鲜质量增长了145.5%;相比于CK组,尿素组(C)的蔬菜鲜质量增长了157.7%。两者结果相近,说明菌剂也能代替一部分肥料促进植物生长,即表明微生物菌肥替代部分化肥是切实可行的。相比于CK组,只施用菌剂的处理(H、M和L)蔬菜鲜质量增幅分别为78.7%、68.6%、55.0%。这可能是由于生物菌肥没有提供足够的氮元素来满足植物生长及合成蛋白质的需要[23],导致单独使用P. polymyxa菌肥的增产相较于尿素做肥料时效果较差。相比于CK组,灭活的菌肥处理组(C+SM)蔬菜鲜质量增幅为96.3%,增产效果相较于C+M处理组较差。这可能是由于菌肥中的P. polymyxa在生长过程中分泌植酸酶等植物生长物质,促进了植物的生长[24]。
与对照组CK相比,处理组C、C+M、C+SM均能明显提高蔬菜的质量,增幅分别为87.7%、84.9%、74.0%,处理组H、M、L的增幅分别为17.8%、13.7%、12.3%。因此,微生物菌肥同化肥混用能有效提高植物的质量,单独施用微生物菌肥对植物质量增产有限。在蔬菜株高上,施用化肥的3个处理组C、C+M和C+SM间无明显差距,只施用微生物菌肥的3个处理组H、M、L的植物株高明显低于施用化肥组,故认为施用化肥可有效提高蔬菜株高。 2) P. polymyxa菌肥对蔬菜硝酸盐含量的影响。图9为不同处理组中蔬菜硝酸盐的含量,表明仅施用化肥处理组(C)蔬菜的硝酸盐积累量最高,为1.74 g·kg?1。这说明施加氮肥会造成蔬菜中氮素明显增加。在相同施氮水平下,C+M处理组蔬菜硝酸盐含量为1.47 g·kg?1,相比于只施加尿素的处理组C,蔬菜内硝酸盐积累降低了15.3%。P. polymyxa在生长过程中会消耗氮素产生氨基酸、酯类等物质[25]。由于植物在利用土壤中的氨基酸这一过程中会消耗较少的能量,所以植物会优先吸收土壤中氨基酸。P. polymyxa将土壤中氮素消耗转变为氨基酸,既能减少蔬菜中硝酸盐的积累,又能提高蔬菜的产量[26-27]。这可能是微生物菌肥降低蔬菜硝酸盐积累的原因。
3) P. polymyxa菌肥对蔬菜维生素C含量的影响。维生素C是蔬菜品质的重要评估指标。分析蔬菜中维生素C的含量,有助于鉴定微生物菌肥对蔬菜品质的影响[28]。图10为不同处理组中蔬菜维生素C的含量,施用微生物菌肥处理组(H)蔬菜维生素含量最高。相比于空白处理组CK,蔬菜中维生素C的含量增加了59.1%;相比于只施用尿素的处理组C,蔬菜中的维生素C含量增加了34.2%。施用化肥能提高蔬菜的产量,但无法有效提高蔬菜品质,而微生物菌肥在提高蔬菜品质上有明显的优势。