Enhancing the compost maturation of deer manure and corn straw by supplementation via black liquor

Revealing novel insights into the enhancement of quality in black tea processing through microbial intervention

Black tea is highly favored by consumers worldwide, with enzymatic reactions being recognized as a pivotal factor influencing tea quality. The role of microorganisms in shaping the composition of black tea has emerged as a focus of research due to their involvement in enzyme catalysis and metabolic processes. In this study, full-length amplicon sequencing combined with qPCR more accurately reflected microbial profile, and Pantoea, Pseudomonas, Paucibacter, and Cladosporium were identified as the main microbial genera. Moreover, by comprehensively analyzing color, aroma, and taste components over time in black tea samples, correlations were established between the dominant genus and various quality factors. Notably, peroxidase activity levels, total soluble sugar content, and tea pigments concentration exhibited significant associations with the dominant genus. Consequently, this microbiological perspective facilitated the exploration of driving factors for improving black tea quality while establishing a theoretical foundation for quality control in industrial production.

Biochar promotes compost humification by regulating bacterial and fungal communities

Introduction

Humus can be formed during composting through biological pathways, nonetheless, the mechanisms through which bacterial and fungal communities govern the development of humus in compost with the addition of biochar remain uncertain.

Methods

In this study, compost with cow dung and maize stover as feedstock was employed as a control group, and compost with 10% biochar added on top of the feedstock was adopted as a treatment group to investigate the effect of bacterial and fungal communities on humus formation during biochar composting.

Results and Discussion

The results demonstrated that the humic acid content increased by 24.82 and 25.10% at the cooling and maturation stages, respectively, after adding biochar. Besides, the degree of polymerization content in the maturation stage was elevated by 90.98%, which accelerated the humification process of the compost. During the thermophilic and maturity stages, there was a respective increase of 51.34 and 31.40% in reducing sugar content, suggesting that the inclusion of biochar could furnish ample reducing sugar substrate for the Maillard reaction. The addition of biochar reduced the number of humus precursor-associated genera by 35, increased the number of genera involved in humus synthesis by two, and enhanced the stability of the cross-domain network between bacteria and fungi, which confirms that microorganisms contribute to the humification process by decreasing humus precursor consumption as well as increasing humus synthesis with the addition of biochar. Additionally, adding biochar could enhance the humification capacity of the compost pile by dominating the Maillard reaction with reducing sugars as the substrate and strengthening the function of humus synthesis-associated genera. This study enhances our comprehension of the regulatory pathways of biochar in the humification process during composting.

Effect of thermal treatment of illite on the bioavailability of copper and zinc in the aerobic composting of pig manure with corn straw

The large amount of various types of heavy metals in animal manure applied to agricultural field has caused severe threat to the ecosystems of soil environments. In this study, the effect of thermal treatment of illite on the bioavailability of copper (Cu) and zinc (Zn) in the aerobic composting of pig manure with corn straw biochar was investigated. The objectives of this study were to characterize the variations in the bioavailability of Cu and Zn in the aerobic composting of pig manure added with illite treated with high temperatures and to identify the relatively dominant microbes involved in the formation of humus and passivation of heavy metals in pig manure composting based on 16S rRNA high-throughput sequencing analysis. The results showed that in comparison with the raw materials of pig manure, the bioavailability of Zn and Cu in the control and three experimental composting groups, i.e., group I (with untreated illite), group I-2 (with illite treated under 200°C), and group I-5 (with illite treated under 500°C), was decreased by 27.66 and 71.54%, 47.05 and 79.80%, 51.56 and 81.93%, and 58.15 and 86.60%, respectively. The results of 16S rRNA sequencing analysis revealed that in the I-5 group, the highest relative abundance was detected in Fermentimonas, which was associated with the degradation of glucose and fructose, and the increased relative abundances were revealed in the microbes associated with the formation of humus, which chelated with Zn and Cu to ultimately reduce the bioavailability of heavy metals and their biotoxicity in the compost. This study provided strong experimental evidence to support the application of illite in pig manure composting and novel insights into the selection of appropriate additives (i.e., illite) to promote humification and passivation of different heavy metals in pig manure composting.

Enhancing C and N turnover, functional bacteria abundance, and the efficiency of biowaste conversion using Streptomyces-Bacillus inoculation

Microbial inoculation plays a significant role in promoting the efficiency of biowaste conversion. This study investigates the function of Streptomyces-Bacillus Inoculants (SBI) on carbon (C) and nitrogen (N) conversion, and microbial dynamics, during cow manure (10% and 20% addition) and corn straw co-composting. Compared to inoculant-free controls, inoculant application accelerated the compost's thermophilic stage (8 vs 15 days), and significantly increased compost total N contents (+47%) and N-reductase activities (nitrate reductase: +60%; nitrite reductase: +219%). Both bacterial and fungal community succession were significantly affected by DOC, urease, and NH4+-N, while the fungal community was also significantly affected by cellulase. The contribution rate of Cupriavidus to the physicochemical factors of compost was as high as 83.40%, but by contrast there were no significantly different contributions (∼60%) among the top 20 fungal genera. Application of SBI induced significant correlations between bacteria, compost C/N ratio, and catalase enzymes, indicative of compost maturation. We recommend SBI as a promising bio-composting additive to accelerate C and N turnover and high-quality biowaste maturation. SBI boosts organic cycling by transforming biowastes into bio-fertilizers efficiently. This highlights the potential for SBI application to improve plant growth and soil quality in multiple contexts.

Bentonite addition enhances the biodegradation of petroleum pollutants and bacterial community succession during the aerobic co-composting of waste heavy oil with agricultural wastes

Soil contamination with petroleum significantly threatens the ecological equilibrium and human health. In this context, aerobic co-composting of waste heavy oil with agricultural wastes was performed in the present study to remediate petroleum pollutants through four treatments: CK (control), T1 (petroleum pollutant), T2 (petroleum pollutant with bentonite), and T3 (petroleum pollutant with humic acid-modified bentonite). Comprehensive analyses were conducted to determine the physicochemical parameters, enzymatic activities, removal of petroleum pollutants, microbial community structure, and water-extractable organic matter in different composting systems. Structural equation modeling was employed to identify the key factors influencing the removal of petroleum pollutants. According to the results, petroleum pollutant removal percentages of 44.94%, 79.09%, and 79.67% could be achieved with T1, T2, and T3, respectively. In addition, the activities of polyphenol oxidase (51.21 U/g) and catalase (367.91 U/g), which are the enzymes related to petroleum hydrocarbon degradation, were the highest in T3. Moreover, bentonite addition to the treatment increased the nitrate nitrogen storage in the compost from 10.95 mg/kg in T1 to 18.63 and 17.41 mg/kg in T2 and T3, respectively. Humic acid-modified bentonite could enhance the degree of compost humification, thereby leading to a higher-quality compost product. Collectively, these findings established bentonite addition as an efficient approach to enhance the compost remediation of petroleum pollutants.