The study examined the impact of adding cattle manure to the composting  process of Agaricus bisporus mushroom substrate on compost humification. A  control group CK comprised entirely of Agaricus bisporus mushroom substrate,  while the experimental group CD (70 percent Agaricus bisporus mushroom  substrate and 30 percent cattle manure) comprised the two composting  treatments that were established. The study determined that the addition of  cow dung has promoted the formation of humus components. Particularly,  humic substance (HS-C) and humic acid (HA) increased by 41.3 and 74.7%,  respectively, and the ratio of humic acid to fulvic acid (HA/FA) also increased  by 2.78. It showed that the addition of cow dung accelerated the synthesis  and decomposition of precursors, such as polysaccharides, polyphenols, and  reducing sugars. Thereby promoting the formation of humic acid. Network  analysis revealed that adding cow dung promoted microbial interactions  increased the complexity and stability of the bacterial and fungal symbiotic  network, enhanced cooperation and reciprocity among microbes, and assisted  in transforming fulvic acid (FA) components. Structural equation modeling  (SEM) is a multivariate data analysis method for analyzing complex relationships  among constructs and core indicators. SEM illustrated that introducing cattle  manure into the composting process resulted in alterations to the correlation  between physicochemical parameters and the microbial community, in  addition to humus formation. Polysaccharides are the primary precursors for  polymerization to form HA, which is an essential prerequisite for the conversion  of fulvic acid to humic acid. Additionally, microbes affected the formation of  humus, with bacteria substantially more influential than fungi. These findings  provide new ideas for regulating the degree of humification in the composting  process and have important practical implications for optimizing mushroom  cultivation and composting techniques today. KEYWORDS composting, cattle manure, spent mushroom substrate, humification, precursors, core  microbes OPEN ACCESS EDITED BY Ruiyong Zhang,  Chinese Academy of Sciences (CAS), China REVIEWED BY Zhao Ma,  Shenzhen University, China Shuchi Singh,  University of Illinois at Urbana-Champaign,  United States *CORRESPONDENCE Fengjun Yang yangfengjun@byau.edu.com RECEIVED 24 January 2024 ACCEPTED 09 July 2024 PUBLISHED 18 July 2024 CITATION Yang F, Wang M, Zhao L, Fan B, Sun N, Liu J,  Sun X and Dong Z (2024) The role of cattle  manure-driven polysaccharide precursors in  humus formation during composting of spent  mushroom substrate. Front. Microbiol. 15:1375808. doi: 10.3389/fmicb.2024.1375808 COPYRIGHT © 2024 Yang, Wang, Zhao, Fan, Sun, Liu, Sun  and Dong. This is an open-access article  distributed under the terms of the Creative  Commons Attribution License (CC BY). The  use, distribution or reproduction in other  forums is permitted, provided the original  author(s) and the copyright owner(s) are  credited and that the original publication in  this journal is cited, in accordance with  accepted academic practice. No use,  distribution or reproduction is permitted  which does not comply with these terms. TYPE Original Research PUBLISHED 18 July 2024 DOI 10.3389/fmicb.2024.1375808Yang et al. 10.3389/fmicb.2024.1375808 Frontiers in Microbiology 02 frontiersin.org 1 Introduction Humus constitutes the principal component of soil organic matter,  presenting itself as a complex polymeric compound derived from  various precursors in nature. It forms through a sequence of  biochemical reactions under the influence of microbial activity.  Meanwhile, humus is a crucial indicator of compost quality due to its  ability to keep soil carbon, remediate soil pollution, and promote plant  growth (Wei et al., 2022). Furthermore, humic acid (HA) and fulvic  acid (FA) are the predominant components of humic substances (HS)  and are employed to evaluate the quality of the final compost product.  Moreover, the formation of HS typically passes through two phases:  the first phase is the generation of HS precursor substances, where  microbes decompose organic matter to form HS precursors, including  polyphenols, amino acids, polysaccharides, and reducing sugars  (Fukuchi et al., 2010; Wu et al., 2017a). Precursors are polymerized in  the second phase to produce HS. Microbial action generates HS  precursors via diverse mechanisms, one of which is the phenolic  protein pathway (Zhang et al., 2018), the lignin protein pathway (Qi  et al., 2020), and the Maillard (sugar-amine condensation) pathway  (Zhao et al., 2017c). The cultivation process of edible mushrooms results in a  remarkable amount of residues. The annual production of mushroom  residues in China s

The study examined the impact of adding cattle manure to the composting  process of Agaricus bisporus mushroom substrate on compost humification. A  control group CK comprised entirely of Agaricus bisporus mushroom substrate,  while the experimental group CD (70 percent Agaricus bisporus mushroom  substrate and 30 percent cattle manure) comprised the two composting  treatments that were established. The study determined that the addition of  cow dung has promoted the formation of humus components. Particularly,  humic substance (HS-C) and humic acid (HA) increased by 41.3 and 74.7%,  respectively, and the ratio of humic acid to fulvic acid (HA/FA) also increased  by 2.78. It showed that the addition of cow dung accelerated the synthesis  and decomposition of precursors, such as polysaccharides, polyphenols, and  reducing sugars. Thereby promoting the formation of humic acid. Network  analysis revealed that adding cow dung promoted microbial interactions  increased the complexity and stability of the bacterial and fungal symbiotic  network, enhanced cooperation and reciprocity among microbes, and assisted  in transforming fulvic acid (FA) components. Structural equation modeling  (SEM) is a multivariate data analysis method for analyzing complex relationships  among constructs and core indicators. SEM illustrated that introducing cattle  manure into the composting process resulted in alterations to the correlation  between physicochemical parameters and the microbial community, in  addition to humus formation. Polysaccharides are the primary precursors for  polymerization to form HA, which is an essential prerequisite for the conversion  of fulvic acid to humic acid. Additionally, microbes affected the formation of  humus, with bacteria substantially more influential than fungi. These findings  provide new ideas for regulating the degree of humification in the composting  process and have important practical implications for optimizing mushroom  cultivation and composting techniques today. KEYWORDS composting, cattle manure, spent mushroom substrate, humification, precursors, core  microbes OPEN ACCESS EDITED BY Ruiyong Zhang,  Chinese Academy of Sciences (CAS), China REVIEWED BY Zhao Ma,  Shenzhen University, China Shuchi Singh,  University of Illinois at Urbana-Champaign,  United States *CORRESPONDENCE Fengjun Yang yangfengjun@byau.edu.com RECEIVED 24 January 2024 ACCEPTED 09 July 2024 PUBLISHED 18 July 2024 CITATION Yang F, Wang M, Zhao L, Fan B, Sun N, Liu J,  Sun X and Dong Z (2024) The role of cattle  manure-driven polysaccharide precursors in  humus formation during composting of spent  mushroom substrate. Front. Microbiol. 15:1375808. doi: 10.3389/fmicb.2024.1375808 COPYRIGHT © 2024 Yang, Wang, Zhao, Fan, Sun, Liu, Sun  and Dong. This is an open-access article  distributed under the terms of the Creative  Commons Attribution License (CC BY). The  use, distribution or reproduction in other  forums is permitted, provided the original  author(s) and the copyright owner(s) are  credited and that the original publication in  this journal is cited, in accordance with  accepted academic practice. No use,  distribution or reproduction is permitted  which does not comply with these terms. TYPE Original Research PUBLISHED 18 July 2024 DOI 10.3389/fmicb.2024.1375808Yang et al. 10.3389/fmicb.2024.1375808 Frontiers in Microbiology 02 frontiersin.org 1 Introduction Humus constitutes the principal component of soil organic matter,  presenting itself as a complex polymeric compound derived from  various precursors in nature. It forms through a sequence of  biochemical reactions under the influence of microbial activity.  Meanwhile, humus is a crucial indicator of compost quality due to its  ability to keep soil carbon, remediate soil pollution, and promote plant  growth (Wei et al., 2022). Furthermore, humic acid (HA) and fulvic  acid (FA) are the predominant components of humic substances (HS)  and are employed to evaluate the quality of the final compost product.  Moreover, the formation of HS typically passes through two phases:  the first phase is the generation of HS precursor substances, where  microbes decompose organic matter to form HS precursors, including  polyphenols, amino acids, polysaccharides, and reducing sugars  (Fukuchi et al., 2010; Wu et al., 2017a). Precursors are polymerized in  the second phase to produce HS. Microbial action generates HS  precursors via diverse mechanisms, one of which is the phenolic  protein pathway (Zhang et al., 2018), the lignin protein pathway (Qi  et al., 2020), and the Maillard (sugar-amine condensation) pathway  (Zhao et al., 2017c). The cultivation process of edible mushrooms results in a  remarkable amount of residues. The annual production of mushroom  residues in China s