Effect of Chinese medicinal herbal residues compost on tomato and Chinese cabbage plants: Assessment on phytopathogenic effect and nutrients uptake.

Chinese medicinal herbal residues (CMHRs) are known for their antipathogenic properties due to the presence of bioactive compounds. Hence, CMHRs could be used as a potential resource to produce biofertilizer with antipathogenic properties for agricultural applications. In this study, a novel approach was used by utilizing the waste-derived biofertilizer, i.e., CMHRs compost (CMHRC) as a nutrient supplier as well as an organic bioagent against Alternaria solani (A. solani) and Fusarium oxysporum (F. oxysporum) on tomato (Lycopersicon esculentum) and Chinese cabbage (Brassica rapa subsp. Chinensis) plants. The experiments were conducted under greenhouse conditions using locally collected acidic soil wherein 2%, 5% and 10% CMHRC (dry weight) along with 5% food waste compost were used as treatments. In addition, only soil and soil with phytopathogens were used as control treatments. The results suggested that amending the compost into acidic soil significantly increased the pH to a neutral level along with enhanced uptake of nutrients. Among all the treatments, 5% CMHRs compost addition increased the tomato plant biomass production to 4.9 g/pot (dry weight) compared to 2.2 g/pot in control. A similar trend was observed in Chinese cabbage plants and the improved plant biomass production could be attributed to the combined effect of strong nutrient absorption ability by healthy roots and enhanced nutrient supply. At 5% CMHRC application rate, the nitrogen uptake by tomato and Chinese cabbage plants increased by 78% and 62%, respectively, whereas phosphorous uptake increased by 75% and 25%, respectively. The reduction in A. solani by 48% and F. oxysporum by 54% in the post-harvested soil of 5% CMHRC treatment against the control demonstrated the anti-phytopathogenic efficiency of CMHRC compost. Hence, the present study illustrates the beneficiary aspects of utilizing CMHRs to produce biofertilizer with anti-phytopathogenic properties which can be safely used for tomato and Chinese cabbage plant growth.

Comparison of the basic processes of aerobic, anaerobic, and aerobic-anaerobic coupling composting of Chinese medicinal herbal residues.

Chinese medicinal herbal residues (CMHRs) are waste generated after extracting Chinese medicinal materials, and they can be used as a renewable bioresource. This study aimed to evaluate the potential of aerobic composting (AC), anaerobic digestion (AD), and aerobic-anaerobic coupling composting (AACC) for the treatment of CMHRs. CMHRs were mixed with sheep manure and biochar, and composted separately under AC, AD, and AACC conditions for 42 days. Physicochemical indices, enzyme activities, and bacterial communities were monitored during composting. Results showed that AACC- and AC-treated CMHRs were well-rotted, with the latter exhibiting the lowest C/N ratio and maximal germination index (GI) values. Higher phosphatase and peroxidase activities were detected during the AACC and AC treatments. Better humification was observed under AACC based on the higher catalase activities and lower E4/E6. AC treatment was effective in reducing compost toxicity. This study provides new insights into biomass resource utilisation.

Highly efficient glucose production from raw non-pretreated Chinese medicinal herbal residues via the synergism of cellulase and amylolytic enzymes.

Available literature on Chinese medicinal herbal residues (CMHRs) bioconversion highlights pretreatment prior to saccharification with cellulase without considering the presence of starch constituent. Herein, four commonly found CMHRs were tested for starch content, and it was found they all contained starch with content ranging from 4.74% to 16.78%. Hydrolysis of raw CMHRs with combined cellulase and amylolytic enzymes yielded increments of 16.85% to 26.51% in 48-h glucan conversion compared to cellulase alone. Further study showed 48-h glucan conversion of raw CMHRs outperformed that pretreated by water-ethanol successive extraction, ultrasound and acid, but underperformed alkali-pretreated CMHRs. Although increasing 48-h glucan conversion in the range of 7.40% to 24.10% compared to raw CMHRs, alkaline pretreatment demonstrated low glucose recovery and incurred additional cost, making it unfavorable. Saccharification of the four raw CMHRs with combined enzymes seems like a preferred option considering the elimination of high-cost pretreatment step.

Development of a compound microbial agent beneficial to the composting of Chinese medicinal herbal residues.

This study was aimed at developing a compound microbial agent to facilitate the composting of Chinese medicinal herbal residues (CMHRs). Different microbial agents were inoculated into a mixture of CMHRs, sheep manure, and biochar and composted for 42 days. The results demonstrated that the compound microbial agent (K1 + P1 + N4) inoculated in T1 can extend the thermophilic period during composting. Compared with control check (CK), the total nutrient contents of the vaccinated groups increased by 5.45-28.54%, and T1 had the highest value. The total organic carbon degradation rate and germination index of T1 were 1.95 and 1.03 times higher than those of the control. Moreover, significant increases in the abundance and diversity of the microbial community were also found in T1. Consequently, using K1 + P1 + N4 as a microbial agent for the composting of CMHRs is recommended, and this research provides a new idea to solve the problem of waste of CMHRs.

[Effect of Co-composting of Chicken Manure with Chinese Medicinal Herbal Residues on Antibiotic Resistance Genes].

Livestock manure is an important pathway by which antibiotic resistance genes (ARGs) enter the environment. To reduce the occurrence of antibiotic resistance genes in manures, we studied the variations of ARGs and mobile gene elements (MGEs) during the 46-day co-composting of chicken manure with Chinese medicinal herbal residues. The abundance of 100 ARGs and 5 MGEs were measured by Real-Time Quantitative PCR with 0, 3, 7, 14, 28, and 46 d co-composting. We detected 21 ARGs, 2 integrase genes (intI1 and intI2), and 3 transposase genes (tnpA-01, tnpA-02, and tnpA-03). The abundance of 5 MGEs significantly declined with co-composting time, particularly tnpA-01 and tnpA-02, which were reduced by two orders of magnitude. The abundance of aacA/aphD and aadE were significantly reduced (P<0.05) in aminoglycoside resistance genes. In ß-lactam resistance genes, the strongest relationships were demonstrated between blaOXA1 and compost days (P=0.016), and the removal rate was 78.63%. The average removal rate was 90.39% for amide resistance genes, which decreased significantly with composting time. The removal ratios were different among tetracycline resistance genes. For example, the removal ratios of tetG and tetR were 99.77% and 31.72%, respectively. The highest removal rate of qnrD was 99.89%. The removal rate of sulⅢ was as high as 99.88%, while sulⅠ showed an increasing trend. Correlations between ARGs and MGEs were significant correlation for tnpA-01 and ARGs (P<0.05). The trend of ARGs with composting time indicates that the composting of Chinese medicine residues and chicken manure can significantly reduce the abundance of ARGs, thus reducing the risk of ARGs being distributed via livestock manure application.

Chinese medicinal herbal residues as a bulking agent for food waste composting.

This study aimed to co-compost Chinese medicinal herbal residues (CMHRs) as the bulking agent with food waste (FW) to develop a high value antipathogenic compost. The FW, sawdust (SD) and CMHRs were mixed at three different mixing ratios, 5:5:1, 2:2:1 and 1:1:1 on dry weight basis. Lime at 2.25% was added to the composting mix to buffer the pH during the composting. A control without lime addition was also included. The mixtures were composted in 20-L in-vessel composters for 56 days. A maximum of 67.2% organic decomposition was achieved with 1:1:1 mixing ratio within 8 weeks. The seed germination index was 157.2% in 1:1:1 mixing ratio, while other ratios showed <130.0% and the treatment without lime showed 40.3%. Therefore use of CMHRs as the bulking agent to compost food waste at the dry weight ratio of 1:1:1 (FW: SD: CMHRs) was recommended for FW-CMHRs composting.

Fate of antibiotic resistance genes and mobile genetic elements during anaerobic co-digestion of Chinese medicinal herbal residues and swine manure.

Swine manure is an important reservoir for antibiotic resistance genes (ARGs) but anaerobic co-digestion (AcoD) can potentially reduce the abundance of these ARGs. However, few studies have considered the effects of Chinese medicinal herbal residues (CMHRs) on the variations in ARGs and mobile genetic elements (MGEs) during AcoD. Thus, this study explored the fate of ARGs and MGEs during the AcoD of CMHRs and swine manure. The results showed that CMHRs effectively reduced the abundances of the main ARGs (excluding ermF, qnrA, and tetW) and four MGEs (by 36.7-96.5%) after AcoD. Redundancy analysis showed that changes in the bacterial community mainly affected the fate of ARGs rather than horizontal gene transfer by MGEs. Network analysis indicated that 17 bacterial genera were possible hosts of ARGs. The results of this study suggest that AcoD with CMHRs could be employed to remove some ARGs and MGEs from swine manure.

Fungal community and cellulose-degrading genes in the composting process of Chinese medicinal herbal residues.

The fungal community and the population of 16S rRNA, 18S rRNA and cellulose-degrading genes during the 30-day composting process of Chinese medicinal herbal residues were investigated using Illumina MiSeq and quantitative real-time PCR. An obvious succession of fungal communities occurred during the composting process. Unidentified fungi predominated in the raw materials. As composting progressed, Ascomycota became the most dominant phylum, with Aspergillus being the most dominant genus, and Aspergillus fumigatus making up 99.65% of that genus. Because of the inoculation of cellulolytic fungi in the mature stage, the cellulose degradation rate in inoculation groups was faster and the relative abundances of Aspergillus and the glycoside hydrolase family 7 genes were significantly higher than those in the control groups. These indicated that the fungal inoculants facilitated the degradation of cellulose, increased cellulolytic fungi and optimized the community structure.

Behavior of antibiotic resistance genes during co-composting of swine manure with Chinese medicinal herbal residues.

Swine manure is considered to be a reservoir for antibiotic resistance genes (ARGs) but little is known about the variations in ARGs during the co-composting of swine manure with Chinese medicinal herbal residues (CMHRs). Thus, this study explored the effects of CMHRs on the variations in ARGs during co-composting with swine manure. The results showed that CMHRs could reduce effectively most of the targeted ARGs (0.18-2.82logs) and mobile genetic elements (MGEs) (0.47-3.34logs). The correlations indicated that CMHRs might decrease the spread of ARGs via horizontal gene transfer. Redundancy analysis showed that the bacterial communities had more important effects on the variations in ARGs compared with environmental factors and MGEs. The results of this study demonstrate that CMHRs can decrease the abundances of ARGs and MGEs, as well as reducing the risk of ARGs spreading during the application of compost products to farmland.

Effect of Chinese medicinal herbal residues on microbial community succession and anti-pathogenic properties during co-composting with food waste.

This study investigated the antimicrobial properties of Chinese medicinal herbal residues (CMHRs) during its co-composting with food waste (FW) in two different ratios along with a control. Inhibition on total microbial population were assessed while the numerically dominant microbes were isolated and their antagonistic effects were assessed. Results indicate that the active ingredients persist in the composting mass did not affect the microbes unspecifically as revealed from almost similar bacterial and fungal populations. Rather specific inhibitory activities against Alternaria solani and Fusarium oxysporum were observed. Apart from the CMHR-born active compounds, CMHR-induced changes in the antagonistic and mycoparasitic abilities of the bacteria and fungi also contribute to the specific inhibition against the tested pathogens. Therefore use of CMHRs during the composting of CMHRs enhances its antipathogenic property resulting in an anti-pathogenic compost.

[Efficiency of Aerobic Co-composting of Urban Sludge and Chinese Medicinal Herbal Residues].

With Chinese medicinal herbal residues and municipal sludge as raw materials for co-composting experiment, the effect of the material ratio and addition time of Chinese medicinal herbal residues on the composting efficiency were investigated, including the change of the temperature, organic matter, ammonia nitrogen, and activity of protease. The best composting conditions were determined based on the results. The experimental results showed that the temperature of the pile was raised in the presence of 60 g Chinese medicinal herbal residues as carbon source and 300 g municipal sludge, the ammonia volatilization was reduced and the activity of protease was improved. The ammonia volatilization was reduced by 35.9% and the activity of protease was increased by 80.5% in 15 d, respectively. Especially, in the early stage, addition of Chinese medicinal herbal residues as conditioner could increase the organic matter degradation. Thus, the composting process was accelerated. Changes in the UV-visible and fluorescence characteristics of dissolved organic matter (DOM) during the co-composting process were discussed. The treatment with Chinese medicinal herbal residues improved the maturity of the compost. Moreover, phospholipid fatty acid (PLFA) method was used to estimate the microbial community structure changes. It showed that the number of microbial community such as fungi and Gram negative bacteria increased with addition of Chinese medicinal herbal residues.

Evaluation of humic substances during co-composting of food waste, sawdust and Chinese medicinal herbal residues.

Humification during co-composting of food waste, sawdust and Chinese medicinal herbal residues (CMHRs) was investigated to reveal its correlation with compost maturity. Food waste, sawdust and CMHRs were mixed at 5:5:1 and 1:1:1 (dry weight basis) while food waste:sawdust at 1:1 (dry wt. basis) served as control. Lime at 2.25% was added to all the treatments to alleviate low pH, and composted for 56 days. Humic acid/fulvic acid (HA/FA) ratio increased to 0.5, 2.0 and 3.6 in the control and treatment at 5:5:1, and 1:1:1 mixing ratio, respectively at the end of composting. The decrease in aliphatic organics in HA demonstrated the degradation of the readily available organics, while an increase in aromatic functional groups indicated the maturity of compost. Disappearance of hemicellulose and weak intensity of lignin in the CMHRs treatments indicated that the lignin provided the nucleus for HA formation; and the CMHRs accelerated the compost maturity.