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This study aims to assess the effect of different carbon-to-phosphorus (C:P) ratios on phosphorus (P) fractions transformation, bacterial community succession and microbial P-solubilizing function in kitchen waste composting with rock phosphate (RP) amendment and phosphate-solubilizing bacteria (PSB) inoculation. Results indicated that initial C:P ratio at 50 enhanced organic carbon degradation, available P (AP) accumulation, the amount of PSB and pqqC gene abundance in composting but higher C:P ratio increased microbial biomass phosphorus (MBP) content. Redundancy analysis showed C:P ratios, PSB amount and pqqC gene abundance greatly affected bacterial community diversity and composition. Network analysis indicated that lower C:P ratio enhanced the interaction frequency in core bacterial network for AP transformation. Variance partitioning analysis abiotic factors contributed more to MBP and AP conversion. The study revealed that C:P ratio could directly drive PSB to regulate P fractions and the accumulation of MBP or AP in P-enriched composting.

Superphosphate fertilizer (SSP) as an additive can reduce the nitrogen loss and increase available phosphorus in composting but few studies investigated the effect of SSP addition on heavy metal and microbial communities. In this study, different ratios (10%, 18%, 26%) of SSP were added into pig manure composting to assess the changes of heavy metal (Cu, Mn, As, Zn, and Fe) fractions, bacterial and fungal communities as well as their interactions. SSP addition at 18% had lower ecological risk but still increased the bioavailability of Cu, Mn, and Fe in composts compared to control. Adding 18% SSP into compost decreased bacterial number and increased the fungal diversity compared to CK. Redundancy analysis indicated heavy metal fractions correlated significantly with bacterial and fungal community compositions in composting with 18% SSP. Network analysis showed adding 18% SSP increased microbial interaction and positive cooperation especially enhanced the proportion of Proteobacteria and Ascomycota.

This study was to investigate the effects of different aeration rates on phosphorus (P) conversion and bacterial community dynamics in P-enriched composting by 16S rRNA gene sequencing, sequential P fractionation, network analysis and structural equation model (SEM). Results indicated that Olsen P content increased by 138 %, 150 %, 121 % after composting with aeration rate (L kg

This study investigated the changes of phosphorus (P) fractions, bacterial community and their response to available P or carbon (C):P during composting with different rock phosphate (RP) addition levels. Results showed that adding RP at 10% or 15% promoted the rise of temperature, maturity and Olsen P accumulation in composting, which had a higher amount of RP solubilization than other groups. Available P changed bacterial composition and decreased diversity in composts. RP solubilization efficiency was negatively correlated to C:P ratio and the highest (22.7%) when 10% RP was added, in which bacterial community changed from "function redundancy" to "intensive P-solubilization". Low C:P ratio (〈300) increased the RP solubilization ratio especially within 135-160. Therefore, this study proposed that adding P-rich substrates to decrease C:P ratio could regulate P-solubilizers' activity for increasing RP solubilization efficiency during composting.

This study was conducted to assess the effect of thermophilic actinomycetes inoculation on the lignocellulose degradation, enzyme activities and microbial community during different types of straw composting from wheat, rice, corn and soybean. The results showed that actinomycetes inoculation not only changed the structure of actinomycetic and bacterial community but also accelerated the degradation of cellulose, hemicellulose and lignin and increased the key enzymes activities including CMCase, Xylanase, manganese peroxidase, lignin peroxidase and laccase during composting particularly from wheat straw and rice straw. The key enzyme and physiochemical parameters which affected organic fractions degradation have been identified by redundancy analysis. The combined application of actinomycete inoculation and urea addition as a source of nitrogen was suggested to regulate the key enzyme activities and lignocellulose degradation, which lays a foundation for effectively managing organic wastes from different types of crop straws by composting.

Composting is widely used as an easily operated and economical method to manage organic wastes. However, the long residence time of composting impedes the recycling nutrients from large amounts of organic wastes produced every day. In this study, the intelligent biodrying + continuous dynamic trough (IB + CDT) was created and used in China’s first urban and rural organic waste treatment and utilization demonstration center in Suzhou city. Results showed that IB + CDT composting had higher temperature, more reduction of moisture than windrow composting, enhancing 40% of composting efficiency. Primary fermentation of the IB + CDT composting in the indoor conditions could achieve the harmless treatment (GI > 80%) of compost within 12 days. The IB + CDT composting product enhanced 17% soil organic matter and 11% available nitrogen. The IB + CDT composting mode could earn 57.6 USD/ton by recycling organic waste and producing organic fertilizer, leading to a sustainable and profitable mode.

This study investigated effects of high-nitrogen source (urea) (R_UR) and protein-like nitrogen source (chicken manure) (R_CM) on humification process during lignocellulose biomass composting. It demonstrated that decreasing ratio of crude fiber (CF), polysaccharide (PS) and amino acids (AAs) in R_CM (29.75%, 53.93% and 73.73%, respectively) was higher than that in R_UR (14.73%, 28.74% and 51.92%, respectively). Humic substance (HS) concentration increased by 7.51% and 73.05% during R_UR and R_CM composting, respectively. The lower total links, more independent modularization and higher proportion of positive correlations between functional bacteria and organic components was observed with R_CM network than R_UR, indicating that protein-like nitrogen source supply may alleviate competition within bacterial community. Moreover, chicken manure supply favorably selects greater special functional bacterial taxa (Pusillimonas, Pedomicrobium, Romboustia and other 24 genus) related to AAs and stimulates the collaborative division of bacterial community. This is significance for strengthening effective transformation of organic components.

Window composting with inoculation or frequent turning is a superior way to improve traditional composting efficiency. However, the relationship between the innocent treatment in composting with inoculation or turning and microbial dynamics is unclear. Here, the impact of inoculation and turning for full scale composting on core bacterial community and their co-occurrence network as well as harmless level were compared by network analysis. Results showed that composts with both inoculation and turning had 46% increase of total organic carbon degradation compared to traditional composting and decreased the abundance of potential pathogens. The relative abundance of thermophilic bacteria and Galbibacter, Methylocaldum, Steroidobacter, etc. increased during composting with turning and inoculation. Luteimonas, Sphaerobacter, Turicibacter and Flavobacterium as core bacteria had significant difference between control and composting with enhanced innocent treatment efficiency. Network analysis suggested that turning increased the number of indigenous core bacteria and inoculation enhanced the interaction among key bacterial network.

The goals of this study were to identify the key culturable organophosphorus-degrading bacteria (OPDB) that contributed to regulating different phosphorus (P) fractions and evaluate the roles of OPDB and inorganic phosphate-solubilizing bacteria (IPSB) in P transformation during different composting. The results showed that the amounts, incidence and community composition of OPDB for composts from diverse sources were distinctly different but significantly related to temperature and organic matter content. Fifteen key OPDB correlated closely with different P fractions have been selected by redundancy analysis. Two structural equation models were established to compare the roles of OPDB and IPSB on P availability during composting. Variance partitioning further showed that the interactions between IPSB and OPDB communities had a greater impact on P transformation than each independent factor. Therefore, the combined regulation of IPSB and OPDB were suggested to control the transformation of P fractions during composting.

Phosphate additives especially superphosphate can reduce nitrogen loss, and increase phosphorus availability in composting. This study investigated the changes of different heavy metals fractions and their relationship with bacterial community and abiotic factors during pig manure composting with adding equimolar H3PO4, H2SO4 and K2HPO4. Results showed that both acidic and alkaline labile phosphate increased the potential ecological risk of heavy metals compared to control, but K2HPO4 decreased the accumulation of exchangeable Zn and Mn by 12% and 15% than that with H3PO4 and H2SO4 addition. Network analysis showed that K2HPO4 enhanced the proportion of negative links in bacterial species with heavy metals, but H3PO4 decreased the stability of bacterial network. Redundancy analysis demonstrated that pH was the key factor on metal speciation and risk with phosphate additives than bacterial role. The study presented theoretical basis for additive selection in controlling composting nitrogen fixation and environmental risk.

Bacillus presents in most composts as core microbial taxa and is widely used as inoculant in composting. However, the role of Bacillus as phosphate-solubilizing bacteria (PSB) inoculant in composting and the response of indigenous bacterial community are unclear. This study used redundancy analysis (RDA), network analysis and structural equation model (SEM) to investigate the dynamics of phosphorus (P) fractions, bacterial community, and microbial interaction in composting with PSB (Bacillus sp. P6) inoculation. Results indicated that Bacillus inoculation increased Olsen P content, organic matter degradation, and bacterial diversity, benefiting P fractions mobilization during composting. RDA showed that pH was the main factor influencing P fractions transformation and bacterial taxa. Network analysis and SEM revealed that Bacillus indirectly improved the contribution of bacterial community on P mobilization by enhancing microbial interactions. Therefore, Bacillus with P solubilizing function may be a potential inoculant to regulate the biotic process of P transformation.

This study aimed to assess the effect of phosphate-solubilizing bacteria (PSB) application and inoculation methods on rock phosphate (RP) solubilization and bacterial community during composting. The results showed that PSB inoculation in different stages of composting, especially both in the beginning and cooling stages, not only improved the diversity and abundance of PSB and bacterial community, but also distinctly increased the content of potential available phosphorus. Redundancy analysis indicated that the combined inoculation of PSB in the initial stage with higher inoculation amount and in the cooling stage with lower inoculation amount was the best way to improve the inoculation effect and increase the solubilization and utilization of RP during composting. Besides, we suggested three methods to improve phosphorus transformation and long-term utilization efficiency in composts based on biological fixation of phosphates by humic substance and phosphate-accumulating organisms.

In this study, enriched ammonia-oxidizing bacteria (AOB) were acquired by domesticated cultivation, followed by inoculation into the co-composting of rice straw and chicken manure. The effect of inoculation on nitrogen loss, the succession of bacterial community and the correlation between the key bacteria and environmental factors were investigated. The results showed that inoculation could reduce ammonia emission and nitrogen loss by transforming ammonium into nitrite. Inoculation also increased the amount and abundance of bacterial community. Redundancy analysis showed that indigenous and exogenous bacteria in inoculation group, compared with those in control group, were positively correlated with nitrite but negatively correlated with ammonium, demonstrating that the former contributed to the lower ammonia emission and nitrogen loss. Based on these results, the application of enriched AOB was proposed as a new method of resource recycle and improvement of composting technology.

The study was conducted to investigate the influence of biochar and/or phosphate-solubilizing bacteria (PSB) inoculants on microbial biomass, bacterial community composition and phosphorus (P) fractions during kitchen waste composting amended with rock phosphate (RP). There were distinct differences in the physic-chemical parameters, the proportion of P fractions and bacterial diversity in different treatments. The contribution of available P fractions increased during composting especially in the treatment with the addition of PSB and biochar. Redundancy analysis showed that bacterial compositions were significantly influenced by P content, inoculation and biochar. Variance partitioning further showed that synergy of inoculated PSB and indigenous bacterial communities and the joint effect between biochar and bacteria explained the largest two proportion of the variation in P fractions. Therefore, the combined application of PSB and biochar to improve the inoculation effect and an optimized regulating method were suggested based on the distribution of P fractions.

This study aims to assess the roles of different humin and heavy-metal resistant bacterial community from composting on heavy metal removal. The results showed that the concentration of Cu2+, Zn2+, Ni2+, Pb2+, Cr3+ and Cd2+ decreased with adding the compost-derived humin, but the removal rates were relatively low ( 2”). Structural equation modeling showed that microbial biomass and humin humification are the key factors for the biosorption of heavy metals. Combining humin from maturity phase with heavy-metal resistant bacteria was suggested to control heavy metal pollution in composts.

The aim of this study is to assess the effectiveness of protein-like precursors addition on promoting humification process during lignocellulose-like biomass composting through adding amino acids to compost. The humification indexes of R1 and R2 was significantly higher than that of CK (P < 0.05). The decreasing ratio of Maillard precursor concentration of R2 and R1 was higher than CK. Amino acids addition affected the bacteria community and environmental factors during composting. Variance partitioning analysis showed that humification process was strengthened with environmental factors, bacteria community, Maillard precursors. Structural equation model (SEM) analysis showed that amino acids had substantial impact on promoting humic acid (HA) formation. The combined application of protein-like wastes and lignocellulose-like wastes was suggested to improve carbon sequestration. This study lays a foundation for economically and effectively managing different types of straws by composting.

Development of cold-adapted microbial agent is an efficient approach for composting in low temperature. The study was conducted to evaluate the effect of semi-continuous replacements of compost materials after inoculation (SRMI) on the heat preservation of low temperature composting derived from chicken manure. Results revealed that SRMI could significantly improve the heat preservation of the pile, although the time of start-up in two inoculation groups was approximately the same. Due to the increase in the number of replacements of materials led to the changes in microbial community structures and enzyme activity. Non-metric multidimensional and colorimetric methods indicated that microbial community structures and enzyme activity was completely different in SRMI. Structural equation model was constructed by key factors involved in diversity of the microbial community, enzyme activity, temperature and bio-heat generation. In summary, SRMI decidedly increase the heat preservation time of the pile and start-up efficiency of the low temperature composting.

This study was conducted to assess the abundance, incidence and diversity of the culturable phosphate-solubilizing bacteria (PSB) community during different organic wastes composting. The key PSB affecting different phosphorus (P) fractions and their relationship with environmental variables were analyzed by redundancy analysis (RDA). The results showed that there were distinct differences in amounts, incidence and community composition of PSB for the composts from different sources. Regression analysis demonstrated significant corrections between the density and incidence of PSB and pH, temperature, OM and DOC/DON. Most of culturable PSB showed high percentages of identity with the phyla of Firmicutes and Proteobacteria. There were thirteen key PSB correlated closely (p

This study was conducted to assess the roles of bacterial community in the dissolved organic matters (DOM) transformation during sludge composting. The relationship among the bacterial community, organic acids, diverse components of DOM as well as the indexes of the phytotoxin level and stability of materials was analyzed by regression and redundancy analysis. The results showed that there were significant correlations between the parameters for evaluating compost phytotoxicity and maturity including GI, C/N, SUVA254, SUVA280, E253/203, and A240-400, which led to a new index (PC1) by principal component analysis. PC1 was significantly affected by four components of DOM, acetic and tartaric acids that were correlated with the bacteria community shift, especially seven key bacteria. Based on structural equation modeling, the key bacteria with the ability to degrade tartaric acid exerted more important roles in regulating the transformation of DOM components, which was helpful for the stability and safety of compost.

The study was conducted to investigate the changes in different fractions of phosphorus (P) and the relationship between different P fractions and their corresponding physicochemical parameters during organic wastes composting. There were distinct differences in the concentration of P fractions for the composts generated from different sources, highest in chicken manure and pig manure. The availability P (including water soluble P, Olsen P and citric acid P) declined from 44% to 36% in all composts, except for KW, following the thermophilic phase during composting, while moderately available P and non-available P increased from 48% to 59%. Different P fractions (inorganic P, organic P, Olsen P, water soluble P and citric acid P) were positively correlated with each other. The composts were clustered into two groups in our hierarchical cluster analysis. Conclusively, we suggested an optimized mode of composting based on the characteristics of the P fractions from different raw materials.

Enriched phosphate-solubilizing bacteria (PSB) agent were acquired by domesticated cultivation, and inoculated into kitchen waste composting in different stages. The effect of different treatments on organic acids production, tricalcium phosphate (TCP) solubilization and their relationship with bacterial community were investigated during composting. Our results pointed out that inoculation affected pH, total acidity and the production of oxalic, lactic, citric, succinic, acetic and formic acids. We also found a strong advantage in the solubilization of TCP and phosphorus (P) availability for PSB inoculation especially in the cooling stage. Redundancy analysis and structural equation models demonstrated inoculation by different methods changed the correlation of the bacterial community composition with P fractions as well as organic acids, and strengthened the cooperative function related to P transformation among species during composting. Finally, we proposed a possible mechanism of P solubilization with enriched PSB inoculation, which was induced by bacterial community and organic acids production.

In this study, actinobacteria agent including Streptomyces sp. and Micromonospora sp. were inoculated during chicken manure composting by different inoculation methods. The effect of different treatments on cellulose degradation and the relationship between inoculants and indigenous actinobacteria were investigated during composting. The results showed that inoculation in different stages of composting all improved the actinobacteria community diversity particularly in the cooling stage of composting (M3). Moreover, inoculation could distinctly accelerate the degradation of organic matters (OM) especially celluloses. Redundancy analysis indicated that the correlation between indigenous actinobacteria and degradation of OM and cellulose were regulated by inoculants and there were significant differences between different inoculation methods. Furthermore, synergy between indigenous actinobacteria and inoculants for degradation of OM and cellulose in M3 was better than other treatments. Conclusively, we suggested an inoculation method to regulate the indigenous actinobacteria based on the relationship between inoculants and indigenous actinobacteria and degradation content.

An experiment was conducted to determine the fractions of molecular weights (MW) and the biodegradability of dissolved organic matter (DOM) in mature composts derived from dairy cattle manure (DCM), kitchen waste (KW), cabbage waste (CW), tomato stem waste (TSW), municipal solid waste (MSW), green waste (GW), chicken manure (CM), sludge (S), and mushroom culture waste (MCW). There were distinct differences in the concentration and MW fractions of DOM, and the two measures were correlated. Fraction MW5kDa was the major component of DOM in all mature composts. Determined 5day biochemical oxygen demand (BOD5) of DOM was correlated to the concentration of DOM and all MW fractions except MW5kDa, indicating that the biodegradability of DOM was a function of the content and proportion of fraction MW5kDa. This study suggests that the amount and distribution of low MW fractions affect DOM biodegradability.