微生物菌剂对猪粪堆肥过程中堆肥理化性质和优势细菌群落的影响

  【目的】  掌握猪粪堆肥过程中微生物群落的演替规律与理化指标的相互关系，对提高猪粪堆肥营养品质和加速堆肥进程具有重要的意义。  【方法】  以猪粪和玉米秸秆 (质量比6∶1) 混合物为堆肥原料，耐高温菌剂主要含Acinetobacter pittii、Bacillus subtilis subsp. Stercoris和Bacillus altitudinis。堆体设接种菌剂 (MI) 和未接种 (对照，CK) 两个处理。常规监测堆肥温度和理化指标值，于堆肥开始后第4、12、24和32天采集样品，以16S rRNA高通量测序技术研究堆肥细菌群落的变化。用堆肥第4、12、24和32天采集的新鲜样品制备浸提液，进行紫花苜蓿种子发芽试验。堆肥结束时，测定全氮、全磷和全钾含量，并探讨微生物菌剂对堆肥理化指标和细菌群落演替的影响。  【结果】  接种微生物菌剂可使堆肥高温期提前2天出现，并且能延长高温期2天。堆肥浸提液的促生试验发现，在堆肥24天后紫花苜蓿种子发芽指数 (GI) 大于80%，且MI对幼苗主根的促生能力大于CK (P < 0.05)。随着发酵过程的进行，堆体体积不断缩小，CK和MI中全钾 (TK) 和全磷 (TP) 含量一直呈增加趋势，在堆肥第32天，CK和MI的全磷含量分别为2.28%和2.63%，处理间差异显著 (P < 0.05)，而全钾含量分别为1.81%和1.86%，全氮含量分别为2.65%和2.63%，pH分别为8.72和8.78，处理间差异均不显著。在整个堆肥过程中，MI和CK的pH变化范围分别为8.40～8.95和8.61～8.93；CK和MI中总有机碳 (TOC) 的降解速率在堆肥的4～12和24～32天均表现为MI大于CK，CK和MI的碳氮比 (C/N) 分别为13.28和15.26，差异显著 (P < 0.05)。堆肥过程中在门水平上占据主导地位的细菌群落主要包括 Proteobacteria、Actinobacteria、Firmicutes和Bacteroidetes，在堆肥的高温期 (堆肥24天)，堆体CK和MI中Firmicutes的相对丰富度分别为17.4%和59.8%；在堆肥的升温期、高温期和腐熟期，优势门水平细菌群落Proteobacteria、Firmicutes和Actinobacteria依次演替，且MI堆体中细菌群落的相对丰度均大于CK。属水平优势细菌为Acinetobacter、Lysinibacillus、Solibacillus、Pseudomonas和Flavobacterium，添加微生物菌剂可使Acinetobacter的丰度在堆肥第4天增加21.41%，此外，添加复合微生物可使堆肥第12天的Shannon和Observed species指数增加。相关性分析表明，温度、全N (TN)、TP、TK、TOC及GI与堆体中细菌组成具有显著相关性，而pH和细菌的相关性不显著。  【结论】  在堆体内接种微生物菌剂可显著提高并维持堆肥过程中优势门、属细菌群落的丰度，进而促进堆体升温并延长高温时期，缩短堆肥腐熟周期，加快总有机碳的分解，最终提高堆肥产品中有效磷的含量。复合微生物菌剂在堆肥升温期起主要作用的为Acinetobacter pittii，高温期为Bacillus subtilis subsp. Stercoris和Bacillus altitudinis，我们建议筛选耐高温细菌时应集中在厚壁菌门的芽孢杆菌属。

Effects of microbial inoculation on compost physical and chemical properties and dominant bacterial communities during composting of pig manure

  【Objectives】  Understanding microbial communities and their physicochemical indexes during composting process is important for the screening of efficient strains to improve the nutritional quality and accelerating the composting process.  【Methods】  Pig manure and maize straw were mixed in a mass ratio of 1 to 6 as the testing manure compost. The high temperature resistant microbial inoculums (Acinetobacter pittii, Bacillus subtilis subsp. Stercoris and Bacillus altitudinis) were inoculated in composting piles as the treatment (MI), and the piles without inoculation as control (CK). The temperatures and pH were monitored, and the compost samples were collected on the 4th, 12th, 24th and 32th day since the starting of the composting, and the bacterial community composition was analyzed using 16s rRNA high-throughput sequencing technology. The collected fresh composting samples were also extracted with water, and a germination test of alfalfa seeds was carried out using the extracts. The contents of total N, P and K were determined at the end of composting.  【Results】  Microbial inoculation led to a 2-day advanced and 2-day prolonged thermophilic stage. The seed germination index (GI) was higher than 80% when soaked in the extract from the 24th and 32th day of MI composting, and the promoting effect on the taproot growth of alfalfa seedlings was significantly greater than that of CK (P < 0.05). As fermentation proceeded, the volume of compost piles decreased gradually. On the 32th day, the content of total P in MI (2.63%) was significantly higher than that in CK (2.28%), while the total K, total N and pH were not significantly different between CK and MI. The degradation rate of total organic carbon (TOC) in MI was greater than that in CK on days of 4–12 and 24–32, and the ratios of C/N were 13.28 and 15.26 (P < 0.05), respectively. The dominant bacterial communities at the phylum level included Proteobacteria, Actinobacteria, Firmiutes and Bacteroides, and the abundance of Firmicutes in CK and MI during the thermophilic phase (on day 24) of composting were 17.4% and 59.8% (P < 0.05), respectively. At the phylum level, Proteobacteria, Firmicutes and Actinobacteria were the dominant bacteria community in the temperature rising, thermophilic and maturity stage, and their relative abundances present in MI were higher than those in CK. Acinetobacterium, Lysinibaculus, Solibaculus, Psedomonas and Flavobacterium were dominant bacteria at the genus level, and the addition of microbial inoculums increased the abundance of Acinetobacter by 21.41% on the 4th day. The Shannon and Observed species indices on the 12th day of composting were increased due to microbial inoculation. Correlation analysis showed that temperature, total N, total P, total K, GI and TOC were significantly correlated with bacterial composition, but pH was not.  【Conclusions】  The microbial inoculums could significantly increase and keep the abundance of dominant bacteria at phylum and genus levels during the composting process, accelerating temperature rising and stable, shortening the time needed for composting, stimulating the decomposition of total carbon and increasing the available P content at the end. Acinetobacter Pittii in the microbial inoculation plays a major role in the temperature rising stage of composting, while Bacillus Subtilis Subsp. Stercoris and Bacillus altitudinis in the thermophilic stage. We suggest that screening of high temperature resistant bacteria should focus on the genus of Bacillus in phylum level of Firmicutes.