This research explored the effects of the addition of low doses of aromatic plant biomasses (APBs) on the microbial community and carbon source decomposition in compost. APBs were reported to be capable of altering the composition and function of microbial communities in many environments. However, the effects of APB addition on the compost carbon source metabolism, a process highly linked to the microbial community of compost, were still unclarified, especially when added in small doses. In this study, Cinnamomum camphora biomass was added to the initial compost of Stropharia rugosoannulata cultivation materials, in a mass ratio of 0%, 1%, 2%, and 3%, respectively. The variation in the carbon source contents, the microbial community composition, and the related enzyme activities of the end compost products were measured. The results showed that Cinnamomum camphora biomass addition significantly altered the content of cellulose, hemicellulose, lignin, and protein of compost products, but did not affect the starch and soluble sugar content. Meanwhile, the addition significantly reduced lignin peroxidase and cellulase activities, but increased xylanase and laccase activities, and had no effect on magnesium peroxidase and polyphenol oxidase. Both the bacterial and fungal community compositions were significantly altered by the addition, though the alpha diversity indexes were not significantly changed. The relative abundance of Proteobacteria and Sordariomycetes was significantly increased by the addition, while Acidobacteria, Chloroflexi and Eurotiomycetes significantly decreased. Structural equation modeling found that the variation in the bacterial community composition (0.464 standard total effect) provided a higher contribution to lignocellulose degradation, rather than the fungal community (0.365 standard total effect). A co-occurrence network analysis further revealed that the trade-off between lignin peroxidase and laccase activity, which was induced by the relative abundance variation in Proteobacteria, Actinobacteriota, and Firmicute members, was the main driver in the lignocellulose decomposition variation. This research provides a new insight into the recycling of APB waste, and offers an improvement to mushroom cultivation material compost.

We synthesized a series of quinazolinone derivates as tyrosinase inhibitors and evaluated their inhibition constants. We synthesized 2-(2,6-dimethylhepta-1,5-dien-1-yl)quinazolin-4(3H)-one (Q1) from the natural citral. The concentration, which led to 50% activity loss of Q1, was 103 ± 2 μM (IC50 = 103 ± 2 μM). Furthermore, we considered Q1 to be a mixed-type and reversible tyrosinase inhibitor, and determined the KI and KIS inhibition constants to be 117.07 μM and 423.63 μM, respectively. Our fluorescence experiment revealed that Q1 could interact with the substrates of tyrosine and L-DOPA in addition to tyrosinase. Molecular docking studies showed that the binding of Q1 to tyrosinase was driven by hydrogen bonding and hydrophobicity. Briefly, the current study confirmed a new tyrosinase inhibitor, which is expected to be developed into a novel pigmentation drug.

The increasing production of industrial aromatic plant residues (IAPRs) are potentially environmental risky, and composting is a promising solution to resolve the coming IAPR problems. Carbon source degradation is a basic but important field in compost research; however, we still lack a clear understanding of carbon source degradation and the corresponding relationship to microbial community variation during IAPR composting, which hampers the improvement of IAPR composting efficiency and the promotion of this technology. In this study, samples were chosen on the first day, the 10th day, the 20th day, and the last day during the composting of Cinnamomum camphora leaf IAPRs, and the microbial community composition, main carbon source composition, and several enzyme activities were measured accordingly. The results showed that during composting, the hemicellulose had the highest reduction (200 g kg−1), followed by cellulose (143 g kg−1), lignin (15.5 g kg−1), starch (5.48 g kg−1), and soluble sugar (0.56 g kg−1), which supported that hemicellulose and cellulose were the main carbon source to microbes during composting. The relative abundance of the main bacterial phylum Firmicute decreased from 85.1% to 40.3% while Actinobactreia increased from 14.4% to 36.7%, and the relative abundance of main fungal class Eurotiomycetes decreased from 60.9% to 19.6% while Sordariomycetes increased from 16.9% to 69.7%. Though principal coordinates analysis found that both bacterial and fungal community composition significantly varied during composting (p < 0.05), structure equation modeling (SEM) supported that bacterial composition rather than fungal counterpart was more responsible for the change in carbon source composition, as the standard total effects offered by bacterial composition (−0.768) was about five times the fungal composition (−0.144). Enzyme2 (comprised of xylanase, laccase, cellulase and manganese peroxidase) provided −0.801 standard total effects to carbon source composition, while Enzyme1 (comprised of lignin peroxidase and polyphenol oxidase) had only 0.172. Furthermore, xylanase and laccase were the only two enzymes appeared in co-occurrence network, clustered with nearly all the carbon sources concerned (except starch) in module-II. Xylanase, hemicellulose, and cellulose were linked to higher numbers of OTUs, more than laccase and other carbon sources. In addition, there were 11 BOTUs but only 1 FOTUs directly interacted to xylanase, hemicellulose, and cellulose simultaneously, three of them were Limnochordaceae and two were Savagea, which highlighted the potential core function in lignocellulose degradation provided by bacterial members, especially Limnochordaceae and Savagea. Thus, the results supported that during composting of Cinnamomum camphora leaf IAPRs, the degradation of dominate carbon sources, hemicellulose and cellulose, was mainly driven by bacterial community rather than fungal community. In addition, the bacterial originated xylanase and laccase played potentially core roles in the functional modules. This research clearly investigated the microbial dynamics of carbon source degradation during the composting of Cinnamomum camphora leaf IAPRs, and offers valuable information about and new insight into future IAPRs waste treatment.