Composting To Inactivate Foodborne Pathogens for Crop Soil Application: A Review

Inactivation of Escherichia coli O157:H7 in Dairy Manure Compost with Alkaline Walnut Hull Biochar

Biochar has been used to accelerate heating profiles during composting by increasing oxygenation, which could also reduce microbial pathogens. However, the antimicrobial inactivation of foodborne pathogens in compost, by amending with biochar without increased heating profiles, has not been evaluated. In this study, we examined the ability of biochar to inactivate E. coli O157:H7 (EC) in fresh dairy manure compost by amending with one of four types of biochar. Two slow pyrolysis biochars (high temperature walnut hull biochar [HTWHB], and walnut hull cyclone biochar [WHCB]), and two fast pyrolysis biochars were examined. Compost with 8.1 log CFU/g of EC + 10% amended biochar was held at 22°C and analyzed for EC weekly. The control treatment sustained ca. 8.7 log CFU of EC through week 7; however, the bacterium was not detected by direct plating in WHCB compost (below the detection limit) by day 7, through the entire 49 days (which may be attributed to increased compost alkalinity [i.e., pH 10.76]). Populations of EC in compost supplemented with 10% of the three other biochars sustained EC populations ≥ 9.2 log through the balance of the study. The four biochars were further tested in soil at 17% moisture to determine if concentrations as low as 3.5% could inactivate EC. When 3.5% HTWHB was added to soil, populations were 5.1 log CFU lower than when 10% of the same biochar was amended into dairy compost by week 3. This may indicate that alkaline biochar, amended into lower moisture, soil may be more biocidal than when alkaline biochar is added to high moisture manure compost. The current study demonstrates that highly alkaline walnut hull cyclone biochar is capable of reducing up to 8 log of EC in high moisture fresh compost in only 7 days, while as little as 3.5% alkaline WHCB in 17% moisture soil can reduce 6.7 log of EC in only 14 days. These results may assist farmers in amending compost, manure, cattle feedlots, or soil with biochar to reduce EC, and potentially other pathogens (e.g., Salmonella enterica, Campylobacter jejuni, and Listeria monocytogenes), with the goal of reducing the dissemination of human bacterial pathogens to meat, poultry, and fresh produce.

Effect of thermophilic bacterial complex agents on synergistic humification of carbon and nitrogen during lignocellulose-rich kitchen waste composting

This work reported the effects of thermophilic bacterial agents on degrading persistent lignocellulose and reducing the loss of valuable nitrogen in kitchen waste (KW) composting. The results showed that thermophilic bacterial compound agents improved the high temperature period by 8 days, and increased the ligninase activity by 0.5-3 times during the composting process. The activity of cellulase increased up to 1 time in agent A (Geobacillus, Clostridium caenicola, Haloplasma) adding group by improving the microbial activity of lignocellulosic degradation metabolic pathways. Nitrogen storage increased to 70% in group added with agent B (Clostridium caenicola, Geobacillus, Clostridium sp. TG60-81) by increasing the population abundance of nitrogen-fixing microorganisms such as Bacillus, Hungateiclostridium and Herbaspirillum, and changed amino acid metabolic pathways. In general, agents A and B could increase the thermophilic phase, optimize the microbial community structure, realize the synergistic humification of carbon and nitrogen, and convert KW into mature and high quality fertilizers.

The archaeal and bacterial community structure in composted cow manures is defined by the original populations: a shotgun metagenomic approach

Introduction

Organic wastes are composted to increase their plant nutritional value, but little is known about how this might alter the bacterial and archaeal community structure and their genes.

Methods

Cow manure was collected from three local small-scale farmers and composted under controlled conditions, while the bacterial and archaeal communities were determined using shotgun metagenomics at the onset and after 74 days of composting.

Results

The bacterial, archaeal, methanogen, methanotrophs, methylotroph, and nitrifying community structures and their genes were affected by composting for 74 days, but the original composition of these communities determined the changes. Most of these archaeal and bacterial groups showed considerable variation after composting and between the cow manures. However, the differences in the relative abundance of their genes were much smaller compared to those of the archaeal or bacterial groups.

Discussion

It was found that composting of different cow manures did not result in similar bacterial or archaeal communities, and the changes that were found after 74 days were defined by the original populations. However, more research is necessary to determine if other composting conditions will give the same results.

Enhancing agricultural sustainability through optimization of the slaughterhouse sludge compost for elimination of parasites and coliforms

For a sustainable ecology, slaughterhouse sludge must be managed effectively in preview of the parasitic or coliforms' spill over to the community. In order to determine the effectiveness of a customized biological decomposer solution in lowering the parasitic eggs and coliform bacteria, three composting units (Unit 1, Unit 2, and Unit 3) were treated with its different amounts. Over a period of 60 days, pH, temperature, humidity, number of the parasitic eggs per gram (EPG) of faecal material, viability of eggs, and coliform counts were evaluated. By the fifth day of the composting process, pH had significantly (P < 0.05) increased across all the treatments and then decreased gradually. Also on the 5th day, all three units entered the thermophilic range (> 45 °C), which persisted for 20 days for Unit 3 and 15 days for Units 1 and 2. Humidity levels initially increased significantly (P < 0.05) in all three units (Unit 3 = 71%, Unit 2 = 64%, and Unit 1 = 55%) but then gradually decreased. On day 5, no decrease in EPG in Unit 1 was detected; however, a non-significant (P > 0.05) 12.5% decline in EPG in Unit 2 and Unit 3 was recorded. After that, a significant (P < 0.05) reduction in EPG was observed in all the three treatments until day 25. By day 5, decreased egg viability was significantly (P < 0.05) recorded in Unit 3 (21.43%); in Unit 1 and Unit 2, the decrease was 6.25% and 14.29%, respectively. Additionally, all units showed a significant (P < 0.05) decrease in total coliforms, meeting minimum allowable limit in Unit 2 and 3 on day 10 and on day 15 in Unit 1. The most substantial reduction in faecal coliforms was observed in Unit 3 (from 2.6 log₁₀ to 1.3 log₁₀), followed by Unit 2 (from 2.6 log₁₀ to 1.5 log₁₀), and then Unit 1 (from 2.6 log₁₀ to 1.6 log₁₀). The results of this study support recommendation of advanced composting techniques to eradicate or reduce the abundance of pathogens (parasites and coliforms). Hence, we endorse the value of careful composting procedures in environment-friendly abattoir waste management and agricultural practices through creating pathogen-free, eco-friendly fertilizers to promote both agricultural and environmental sustainability.

Virome and metagenomic sequencing reveal the impact of microbial inoculants on suppressions of antibiotic resistome and viruses during co-composting

Co-composting with exogenous microbial inoculant, presents an effective approach for the harmless utilization of livestock manure and agroforestry wastes. However, the impact of inoculant application on the variations of viral and antibiotic resistance genes (ARGs) remains poorly understood, particularly under varying manure quantity (low 10 % vs. high 20 % w/w). Thus, employing virome and metagenomic sequencing, we examined the influence of Streptomyces-Bacillus Inoculants (SBI) on viral communities, phytopathogen, ARGs, mobile genetic elements, and their interrelations. Our results indicate that SBI shifted dominant bacterial species from Phenylobacterium to thermotropic Bordetella, and the quantity of manure mediates the effect of SBI on whole bacterial community. Major ARGs and genetic elements experienced substantial changes with SBI addition. There was a higher ARGs elimination rate in the composts with low (∼76 %) than those with high manure (∼70 %) application. Virus emerged as a critical factor influencing ARG dynamics. We observed a significant variation in virus community, transitioning from Gemycircularvirus- (∼95 %) to Chlamydiamicrovirus-dominance. RDA analysis revealed that Gemycircularvirus was the most influential taxon in shaping ARGs, with its abundance decreased approximately 80 % after composting. Collectively, these findings underscore the role of microbial inoculants in modulating virus communities and ARGs during biowaste co-composting.

Application of microbial agents in organic solid waste composting: a review

The rapid growth of organic solid waste has recently exacerbated environmental pollution problems, and its improper treatment has led to the loss of a large number of biomass resources. Here, we expound the advantages of microbial agents composting compared with conventional organic solid waste treatment technology, and review the important role of microbial agents composting in organic solid waste composting from the aspects of screening and identification, optimization of conditions, mechanism of action, combination with other technologies and ultra-high-temperature and ultra-low-temperature microbial composting. We discuss the value of microorganisms with different growth conditions in organic solid waste composting, and put forward a seasonal multi-temperature composite microbial composting technology. Provide new ideas for the all-round treatment of microbial agents in organic solid waste in the future. © 2024 Society of Chemical Industry.

A comprehensive study of food waste management and processing in the Czech Republic: Potential health risks and consumer behavior

Food waste is currently a widely discussed phenomenon with significant economic and social consequences. One third of the food produced in the world is wasted at various points along the food supply chain. This article presents a comprehensive study that examines consumer behavior in dealing with food waste and activities in the composting process that enable waste sanitation. The survey conducted as part of this study showed that consumers want to eliminate odors, are concerned about potential infections, and generally sort less food waste. This study suggested that the addition of appropriate additives could be a solution. The results indicated that additives could eliminate negative side effects such as unpleasant odors, the presence of insects and rodents, and act as a prevention of the occurrence of pathogenic organisms. Tea tree oil showed the best positive physical and chemical properties among the additives tested (CaCO3 and citric acid) with a significant effect on inhibiting the growth of bacterial strains such as Salmonella strains and had the strongest antibacterial effect, neutralized unpleasant odors, and stabilized the waste. The use of additives could be a future solution to meet consumer demands, improve the quality of food waste and advance the circular economy to improve the sustainability of agricultural systems.

Effects of slatted frame placed in compost pile on enhancing heat generation and organic matter degradation during high-moisture cow manure composting

Excess moisture content in cow manure inhibits the process of composting. This study examined the effects of introducing a slatted frame on temperature development, organic matter degradation, and moisture content during high-moisture composting. Twelve tons of cow manure was piled individually, and an iron slatted frame with a pipe and a plain frame filled inside with styrofoam was introduced in the treatment and control piles, respectively. Two hours after the start, running leachate via the pipe in the treatment pile was observed, but not in the control pile. The maximum temperatures as well as durations of the temperatures above 55°C of the treatment piles at all seven positions were higher than those of the control piles. In particular, four of the seven positions in the treatment pile exhibited more than twice the duration. Installing the slatted frame improved the organic matter degradation; the values of organic matter loss in the control and treatment were 48.0% and 58.4%, respectively. The final moisture content in the treated compost was 5% lower than that in the control. Overall, the introduction of a slatted frame generated higher temperatures and produced relatively dried and well-degraded compost.

Prevalence, antibiotic resistance and molecular characterization of Staphylococcus aureus in ready-to-eat fruits and vegetables in Shanghai, China

Staphylococcus aureus (S. aureus) is one of the foodborne pathogens. This study aimed to investigate the prevalence of S. aureus in ready-to-eat (RTE) fruits and vegetables in Shanghai, China. We evaluated antibiotic resistance patterns and genetic diversity of isolates through whole genome sequencing. Our findings demonstrated that out of 143 market samples, 47 (32.87%) tested positive for S. aureus, with the prevalence rates ranging from 10% to 57.14% among 12 types of RTE fruits and vegetables. Most isolates were resistant to trimethoprim-sulphamethoxazole, oxacillin, and ampicillin. We identified a total of 15 antibiotic resistance genes associated with resistance to 6 antibiotics, such as fosfomycin, fluoroquinolone, and β-lactam. Adhesion genes and enterotoxin genes, including icaA, icaB, icaC, set, seg, and sec, were also identified. Seven multi-locus sequence types (MLST) were detected, two of which were novel (ST7208 and ST7986). Notably, ST705-t529 (34.04%) and ST6-t701 (27.79%) represented the predominant types of S. aureus. Furthermore, three of the isolates were confirmed to be methicillin-resistant S. aureus by mecA genes. Taken together, our results highlight the high prevalence of S. aureus in RTE fruits and vegetables, posing a potential threat to food safety, particularly due to its high level of antibiotic resistance.

Resistant Bacteria in Broiler Litter Used as Ruminant Feed: Effect of Biotic Treatment

The use of antimicrobial drugs and coccidiostats in poultry farming is widespread, with a significant proportion of these drugs being excreted and released into the environment. The residues of such drugs in poultry litter (PL) can result in the development of antibiotic-resistant bacteria. The impact of different biotic treatments (aerobic, anaerobic, and stacking) on broiler litter (BL) before its use as animal feed has not been studied extensively, nor have the differences between antimicrobial-dependent and independent broiler farms been investigated. This study aimed to determine the resistant bacteria in BL used as ruminant feed before and after litter treatment. The results show that the most resistant bacteria before BL treatment were the Enterococcus species. This study also found that the quantity of amoxicillin-resistant Enterococcus detected in samples from antimicrobial-dependent farms was significantly higher than in those from antimicrobial-independent farms. Additionally, 14% of bacteria were multi-resistant to tetracycline, sulfafurazole, and erythromycin in antimicrobial-independent farm litters, significantly lower than those measured in antimicrobial-dependent broiler farm litter. This study highlights the importance of better understanding, regulating, managing, and using animal waste appropriately to reduce the number of antibiotic-resistant bacteria and minimize the use of antimicrobials that carry high risks for animals, humans, and the environment.

Biochar preparation and evaluation of its effect in composting mechanism: A review

This article provides an overview of biochar application for organic waste co-composting and its biochemical transformation mechanism. As a composting amendment, biochar work in the adsorption of nutrients, the retention of oxygen and water, and the promotion of electron transfer. These functions serve the micro-organisms (physical support of niche) and determine changes in community structure beyond the succession of composing primary microorganisms. Biochar mediates resistance genes, mobile gene elements, and biochemical metabolic activities of organic matter degrading. The participation of biochar enriched the α-diversity of microbial communities at all stages of composting, and ultimately reflects the high γ-diversity. Finally, easy and convincing biochar preparation methods and characteristic need to be explored, in turn, the mechanism of biochar on composting microbes at the microscopic level can be studied in depth.

Yeast community succession in cow dung composting process

Yeast complexes in the composting process of cow dung prepared to fertilize the soil for growing vegetables and fruits were studied. The average abundance of yeasts changed during the four temperature stages of the composting process. The highest abundance of yeasts, 1.38 × 10⁴ cfu/g, was observed in the second stage of heating from 20 to 40 °C; the lowest was studied in the stage with the highest temperature (65 °C), 1.68 × 10³ cfu/g. A total of 19 yeast species were observed and identified: 11 ascomycetes and 8 basidiomycetes, belonging to five subphyla of Fungi: Saccharomycotina (10), Pezizomycotina (1), Agaricomycotina (5), Pucciniomycotina (2), and Ustilaginomycotina (1). The greatest diversity of yeasts was found in the initial (20 °C) and second (heating up to 40 °C) temperature stages of composting (Aureobasidium pullulans (yeast-like fungus), Candida parapsilosis, Candida saitoana, Candida santamariae, Candida tropicalis, Curvibasidium cygneicollum, Cutaneotrichosporon moniliforme, Debaryomyces fabryi, Debaryomyces hansenii, Filobasidium magnum, Kazachstania sp., Moesziomyces bullatus, Naganishia globosa, Papiliotrema flavescens, Rhodotorula mucilaginosa, Scheffersomyces insectosa, Torulaspora delbrueckii, Vanrija musci), and the lowest in the stage of maximum heating (65 °C) (C. parapsilosis, C. tropicalis, Cyberlindnera jadinii).The opportunistic yeasts C. parapsilosis and C. tropicalis were obtained not only in the initial, second and third temperature stages of the composting process, but also in mature compost in the final stage prepared for soil application. This study shows that the cow dung, used in the farm studied did not meet the microbiological safety criteria. The reduction of opportunistic yeast species was not achieved with the composting method used. The likelihood of these species entering agricultural products via compost and soil and developing as endophytes in the internal tissues of fruits is very high. Since some strains of opportunistic Candida species from cow dung exhibited virulent characteristics (they produced hydrolytic enzymes and were resistant to antifungal compounds), additional phenotypic and genetic studies of the compost strains and their comparison with clinical isolates should be pursued.

Biowastes of slaughterhouses and wet markets: an overview of waste management for disease prevention

Slaughterhouse and wet market wastes are pollutants that have been always neglected by society. According to the Food and Agriculture Organization of the United Nations, more than three billion and nineteen million livestock were consumed worldwide in 2018, which reflects the vast amount and the broad spectrum of the biowastes generated. Slaughterhouse biowastes are a significant volume of biohazards that poses a high risk of contamination to the environment, an outbreak of diseases, and insecure food safety. This work comprehensively reviewed existing biowaste disposal practices and revealed the limitations of technological advancements to eradicate the threat of possible harmful infectious agents from these wastes. Policies, including strict supervision and uniform minimum hygienic regulations at all raw food processing factories, should therefore be tightened to ensure the protection of the food supply. The vast quantity of biowastes also offers a zero-waste potential for a circular economy, but the incorporation of biowaste recycling, including composting, anaerobic digestion, and thermal treatment, nevertheless remains challenging.

Co-occurrence pattern of ARGs and N-functional genes in the aerobic composting system with initial elevated temperature

Animal manure is known to harbor antibiotic resistance genes (ARGs). Aerobic composting is a prevalent cost-effective and sustainable method to treat animal waste. However, the effect of initially elevated temperature on antibiotic resistome during the composting process is unclear. In this study composting was subjected to initial external heating (EHC) for a period of 5 days compared to conventional composting (CC). After composting ARGs abundance was significantly reduced by 2.43 log in EHC and 1.95 log in CC. Mobile genetic elements (MGEs) also exhibited a reduction of 1.95 log in EHC and 1.49 log in CC. However, during the cooling phase, the genes resisting macrolide lincosamide and streptogramin B (MLSB) rebounded by 0.04 log in CC. The potential human pathogenic bacteria Pseudomonas (41.5-61.5%) and Actinobacteria (98.4-98.8%) were significantly reduced in both treatments and the bulk of targeted antibiotics were eliminated by 80.74% in EHC and 68.98% in CC. ARGs and N-functional genes (NFGs), mainly denitrification genes, were carried by the same microbial species, such as Corynebacterium sp. and Bacillus sp., of the dominant phylum. Redundancy analysis (RDA) revealed that CC microbial communities played a key role in the enrichment of ARGs while in EHC the variation of ARGs was attributed to the composting temperature. The number of high-risk ARGs was also lower in EHC (4) compared with CC (6) on day 30. These results provide insight into the effects of an initially enhanced temperature on ARGs removal and the relationship between ARGs and NFGs during the composting process.

Static Aerated Composting of African Swine Fever Virus-Infected Swine Carcasses with Rice Hulls and Sawdust

Identifying and ensuring the inactivation of the African Swine Fever virus in deadstock is a gap in the swine industry's knowledge and response capabilities. The results of our study demonstrate that ASFv in deadstock was inactivated using static aerated composting as the carcass disposal method. Replicated compost piles with whole market hogs and two different carbon sources were constructed. In-situ bags containing ASFv-infected spleen tissue were placed alongside each of the carcasses and throughout the pile. The bags were extracted at days 0, 1, 3, 7, 14, 28, 56, and 144 for ASFv detection and isolation. Real-time PCR results showed that DNA of ASFv was detected in all samples tested on day 28. The virus concentration identified through virus isolation was found to be below the detection limit by day 3 in rice hulls and by day 7 in sawdust. Given the slope of the decay, near-zero concentration with 99.9% confidence occurred at 5.0 days in rice hulls and at 6.4 days in sawdust. Additionally, the result of virus isolation also showed that the virus in bone marrow samples collected at 28 days was inactivated.

Fate of Horizontal-Gene-Transfer Markers and Beta-Lactamase Genes during Thermophilic Composting of Human Excreta

Thermophilic composting is a suitable treatment for the recycling of organic wastes for agriculture. However, using human excreta as feedstock for composting raises concerns about antibiotic resistances. We analyzed samples from the start and end of a thermophilic composting trial of human excreta, together with green cuttings and straw, with and without biochar. Beta-lactamase genes bla_CTX-M, bla_IMP, and bla_TEM conferring resistance to broad-spectrum beta-lactam antibiotics, as well as horizontal gene transfer marker genes, intI1 and korB, were quantified using qPCR. We found low concentrations of the beta-lactamase genes in all samples, with non-significant mean decreases in bla_CTX-M and bla_TEM copy numbers and a mean increase in bla_IMP copy numbers. The decrease in both intI1 and korB genes from start to end of composting indicated that thermophilic composting can decrease the horizontal spread of resistance genes. Thus, thermophilic composting can be a suitable treatment for the recycling of human excreta.

Environmental implications, potential value, and future of food-waste anaerobic digestate management: A review

Globally, the valorisation of food waste into digestate through the process of anaerobic digestion is becoming increasingly popular. As a result, a large amount of food-waste digestate will need to be properly utilised. The utilisation of anaerobic digestion for fertiliser and alternative uses is essential to obtain a circular bioeconomy. The review aims to examine the environmental management of food-waste digestate, the value of digestate as a fertiliser and soil conditioner, and the emerging uses and improvements for post-anaerobic digestion reuse of digestate. Odour emissions, contaminants in food waste, emission and leaching of nutrients into the environment, and the regulations, policies, and voluntary initiatives of anaerobic digestion are evaluated in the review. Food-waste digestate can provide essential nutrients, carbon, and bio-stimulants to soils and increase yield. Recently, promising research has shown that digestates can be used in hydroponic systems and potentially replace the use of synthetic fertilisers. The integration of anaerobic digestion with emerging uses, such as extraction of value-added products, algae cultivation, biochar and hydrochar production, can further reduce inhibitory sources of digestate and provide additional economic opportunities for businesses. Moreover, the end-product digestate from these technologies can also be more suitable for use in soil application and hydroponic use.

Composition and contamination of source separated food waste from different sources and regulatory environments

Food waste recycling is needed to create a more sustainable, circular food system; however, the process must be carefully managed to avoid the introduction and build-up of contaminants. We collected and screened source-separated food waste for five classes of contaminants (physical contaminants, heavy metals, halogenated organics, pathogens and antibiotic resistance genes) from two regulatory environments (voluntary vs mandated food separation) to quantify contamination. Physical contamination was frequently found; 57% of samples contained non-compostable waste. Most heavy metals were not detected, and although copper and zinc were present in most samples, they were always below the most stringent global standards for compost. Some samples had detectable halogenated organics, including perfluoroalkyl substances (PFAS), which is cause for concern because some of these accumulate in the food chain. PFBA was detected in 60%, PFHxS in 8% and PFNA in 4% of samples tested. The pathogen Salmonella was present in 3% (2/71) and L. monocytogenes in 11% (8/71) of samples. Shiga toxin-producing E. coli was not detected. Next generation sequencing showed the presence of several genera that contain foodborne pathogens, most commonly Yersinia. Antibiotic resistance genes tet(M) and bla_TEM were present in 96% and 97% of samples respectively, however the last-resort colistin resistance gene mcr-1 was not detected. Overall contamination in our source-separated samples was low, with the exception of some antibiotic resistance genes, however our processing method might have underestimated packaging-associated contamination. Regulatory environment did not affect contamination, but carbon, nitrogen phosphorus, calcium, copper, tet (M), and physical contamination varied by source type.

Bacterial ring rot of potato caused by Clavibacter sepedonicus: A successful example of defeating the enemy under international regulations

BACKGROUND

Bacterial ring rot of potato (Solanum tuberosum) caused by the gram-positive coryneform bacterium Clavibacter sepedonicus is an important quarantine disease threatening the potato industry around the globe. Since its original description in 1906 in Germany, management of ring rot has been a major problem due to the seedborne nature (via seed tubers not true seeds) of the pathogen allowing the bacterium to be transmitted long distances via infected tubers.

DISEASE SYMPTOMS

On growing potato plants: interveinal chlorosis on leaflets leading to necrotic areas and systemic wilt. On infected tubers: vascular tissues become yellowish brown with a cheesy texture due to bacterial colonization and decay.

HOST RANGE

Potato is the main host of the pathogen, but natural infection also occurs on eggplant, tomato, and sugar beet.

TAXONOMIC STATUS OF THE PATHOGEN

Class: Actinobacteria; Order: Actinomycetales; Family: Microbacteriaceae; Genus: Clavibacter; Species: Clavibacter sepedonicus (Spieckermann and Kotthoff 1914) Li et al. 2018.

SYNONYMS (NONPREFERRED SCIENTIFIC NAMES)

Aplanobacter sepedonicus; Bacterium sepedonicum; Corynebacterium sepedonicum; Corynebacterium michiganense pv. sepedonicum; Clavibacter michiganensis subsp. sepedonicus.

MICROBIOLOGICAL PROPERTIES

Gram-positive, club-shaped cells with creamy to yellowish-cream colonies for which the optimal growth temperature is 20-23°C.

DISTRIBUTION

Asia (China, Japan, Kazakhstan, Nepal, North Korea, Pakistan, South Korea, Uzbekistan, the Asian part of Russia), Europe (Belarus, Bulgaria, Czech Republic, Estonia, Finland, Georgia, Germany, Greece, Hungary, Latvia, Lithuania, Norway, Poland, Romania, European part of Russia, Slovakia, Spain, Sweden, Turkey, Ukraine), and North America (Canada, Mexico, USA).

PHYTOSANITARY CATEGORIZATION

CORBSE: EPPO A2 list no. 51. EU; Annex designation I/A2.

Physical, chemical, and microbial contaminants in food waste management for soil application: A review

Currently, 1.3 billion tonnes of food are thrown away each year, most of which are incinerated or landfilled causing large environmental, social, and economic issues. Therefore, the utilisation of food waste as biofertilisers, such as composts and digestates, is a solution to reduce the problems created by incineration and landfilling whilst simultaneously amending soils. The improper disposal of food wastes and bulking materials can contribute to high levels of contaminants within the end-product. Moreover, the food waste and bulking materials, themselves, may contain trace amounts of contaminants. These contaminants tend to have long half-lives, are easily mobile within soil and plants, can accumulate within the food supply chain, and have moderate to high levels of toxicity. This review aims to examine the current and emerging contaminants of high concern that impact the quality of food-waste fertilisers. The paper presents the volume of current and emerging contaminants of plastics, other physical (particulate) contaminants, heavy metals, pesticides, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), per- and polyfluoroalkyl substances (PFAS), and pathogens within food-waste composts and digestates. Due to the large extent of organic chemical contaminants and the unknown level of toxicity and persistence, the risk assessment of organic chemical contaminants in the food-supply chain remains largely unknown. This study has presented available data from literature of various contaminants found in food waste, and composts and digestates derived from food waste, and evaluated the data with current regulations globally. Overall, to reduce contaminants in composts and digestates, more studies are required on the implementation of proper disposal separation, effective composting and digestion practices, increased screening of physical contaminants, development of compostable plastics, and increased regulatory policies on emerging, problematic contaminants. Moreover, examination of emerging contaminants in food-waste composts and digestates is needed to ensure food security and reduce future human-health risks.

A Combined Field–Lab Approach for Assessing Salmonella Infantis Persistence in Broiler Litter in a Stockpile and Composting Sleeve

Broiler litter (BL) is often contaminated by a variety of zoonotic pathogens. This study attempts to assess the persistence of Salmonella enterica serovar Infantis (S. Infantis) in BL based on spatial and temporal variation of physicochemical properties in a stockpile and composting sleeve. A single trial of two pilot-scale setups, ~35 m3 each, included an open static pile (stockpile) and composting in a polyethylene sleeve with forced aeration. The initial water content was adjusted only for the sleeve (~50% w/w) as in a common composting practice. Both systems were monitored weekly and then biweekly during 2 months in 47–53 sampling points each on every campaign. Measurements included temperature, water content, pH, electrical conductivity (EC), gas-phase oxygen, and ammonia, and the collected data were used to construct multiple contour grid maps. Of the stockpile volume, 83, 71, and 62% did not reach the commonly required minimum temperature of 55°C for three consecutive days during the first, second, and third weeks, respectively. Oxygen levels showed a strong gradient across the stockpile, while anaerobic conditions prevailed in the core. Variation was also recorded within the sleeve, but due to the water content adjustment and active aeration, the conditions favored more intense degradation and higher temperatures. Combining the grid maps drawn in this study with decay rate constants recently published for S. Infantis in BL under 36 combinations of temperature, water content, and pH, we assessed the spatial persistence of S. Infantis in the stockpile and the sleeve. Temperature was shown as a major factor, while water content and pH had only a small effect, in the stockpile only. Co-correlations between temperature, water content, EC, and oxygen suggest that selected physicochemical properties may be sufficient for such assessments. Up to 3 weeks would be recommended to achieve 7–8 log10 reduction in Salmonella in a stockpile, while this would be fully achieved within 1 week in a sleeve. This approach of combining high-resolution spatial field sampling along with decay rates of pathogens under controlled lab conditions may improve quantitative microbial risk assessments and future regulations of manure utilization.

Lagoon, Anaerobic Digestion, and Composting of Animal Manure Treatments Impact on Tetracycline Resistance Genes

Increased demand for animal protein is met by increased food animal production resulting in large quantities of manure. Animal producers, therefore, need sustainable agricultural practices to protect environmental health. Large quantities of antimicrobials are used in commercial food animal production. Consequently, antimicrobial-resistant bacteria and the resistance genes emerge and are excreted through feces. Manure management is essential for the safe disposal of animal waste. Lagoons, with or without covers, and anaerobic digesters, with the primary purpose of methane production, and composting, with the primary purpose of producing organic fertilizer, are widely used methods of manure treatment. We reviewed manure management practices and their impact on tetracycline resistance genes. Lagoons are maintained at ambient temperatures; especially uncovered lagoons are the least effective in removing tetracycline resistance genes. However, some modifications can improve the performance of lagoons: sequential use of uncovered lagoons and the use of covered lagoons resulted in a one-log reduction, while post-treatments such as biofiltration following covered lagoon treatment resulted in 3.4 log reduction. Mesophilic digestion of animal manure did not have any significant effect; only a 0.7 log reduction in tet(A) was observed in one study. While thermophilic anaerobic digesters are effective, if properly operated, they are expensive for animal producers. Aerobic thermophilic composting is a promising technology if optimized with its economic benefits. Composting of raw animal manure can result in up to a 2.5 log reduction, and postdigestion composting can reduce tetracycline resistance gene concentration by >80%. In general, manure management was not designed to mitigate antimicrobial resistance; future research is needed to optimize the economic benefits of biogas or organic fertilizer on the one hand and for the mitigation of foodborne pathogens and antimicrobial resistance on the other.

Agricultural practices in Brazilian organic farms and microbiological characteristics of samples collected along the production chain

AIMS

To gather data on agricultural practices in organic farms in Sao Paulo, Brazil, and evaluate their relationship with the microbiological characteristics of samples collected along the production chain.

METHODS AND RESULTS

Practices data were based on field observations and interviews with farmers in 10 selected organic lettuce producing farms. Counts of Enterobacteriaceae and surveys for Salmonella were performed in samples of lettuce (before and after washing), fertilizers, irrigation and washing water, all collected in the same farm. Water samples were also tested for total coliforms and generic Escherichia coli. Isolated Enterobacteriaceae were identified by MALDI-TOF MS. Contamination of lettuce was influenced by some agricultural practices: chicken manure-based fertilization resulted in higher Enterobacteriaceae counts in lettuce when compared to other types of manure, whereas pre-washed lettuces presented lower microbial counts than non-pre-washed samples. Salmonella was detected in one lettuce sample by qPCR. Escherichia coli was detected in all irrigation water samples. All sample types contained Enterobacteriaceae species commonly reported as opportunistic human pathogens.

CONCLUSIONS

The data highlight the need for improvement in the good agricultural practices in the studied farms.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study provides information on agricultural practices and microbiological characteristics of organic lettuce, contributing to the development of more accurate risk assessments.

Impacts of different treatment methods for cattle manure on the spread of faecal indicator organisms from soil to lettuce in Nigeria

AIM

This study investigated impacts of different organic waste treatment methods on reduction and spread of faecal indicator organisms to food crops in a developing country.

METHODS AND RESULTS

Fresh cattle manure was subjected to three different treatments; anaerobic digestion, burning and composting. Escherichia coli, coliforms and nitrogen content of cattle manure were measured before and after treatment in the amended soil and harvested lettuce. All treatments significantly reduced E. coli and coliform counts but differed in the ratio of E. coli or coliforms to nitrogen. Application of the recommended nitrogen dose of 120 kg ha-1 as bioslurry resulted in significantly lower E. coli and coliform contamination of soil than the same nitrogen rate applied as compost or ash. The E. coli content of lettuces grown on soil amended with treated wastes at recommended rates did not differ between treatments but was significantly lower than in lettuces grown on soil amended with untreated manure.

CONCLUSIONS

Treatment of manure before use as an organic fertilizer significantly reduces potential contamination of both soil and food crops with E. coli and coliforms. To best reduce the spread of E. coli from organic fertilizers, manures should be treated by anaerobic digestion.

SIGNIFICANCE AND IMPACT OF THE STUDY

Information from this study quantifies potential risks associated with use of manures in growing food crops by determining the ratio between pathogen content and required nitrogen application rate.

Influence of Manure Application on the Soil Bacterial Microbiome in Integrated Crop-Livestock Farms in Maryland

As a traditional agricultural system, integrated crop-livestock farms (ICLFs) involve the production of animals and crops in a shared environment. The ICLFs in the mid-Atlantic region of the United States practice sustainable manure aging or composting processes to provide an on-farm source of soil amendment for use as natural fertilizer and soil conditioner for crop production. However, crop fertilization by soil incorporation of aged manure or compost may introduce different microbes and alter the soil microbial community. The aim of this study was to characterize the influence of aged or composted manure application on the diversity of soil bacterial community in ICLFs. Soil samples from six ICLFs in Maryland were collected before (pre-crop) and during the season (2020–2021) and used to analyze soil bacterial microbiome by 16S rDNA sequencing. Results showed that both phylum- and genus-level alterations of soil bacterial communities were associated with amendment of aged or composted manure. Particularly, Proteobacteria and Actinobacteria were enriched, while Acidobacteria, Bacteroidetes, Planctomycetes, Firmicutes, and Chloroflexi were reduced after manure product application. Meanwhile, the relative abundance of Bacillus was decreased, while two zoonotic pathogens, Salmonella and Listeria, were enriched by manure amendments. Overall, animal manure amendment of soil increased the phylogenetic diversity, but reduced the richness and evenness of the soil bacterial communities. Although manure composting management in ICLFs benefits agricultural sustainable production, the amendments altered the soil bacterial communities and were associated with the finding of two major zoonotic bacterial pathogens, which raises the possibility of their potential transfer to fresh horticultural produce crops that may be produced on the manured soils and then subsequently consumed without cooking.

Identification and structural analysis of a thermophilic β-1,3-glucanase from compost

β-1,3-glucanase can specifically hydrolyze glucans to oligosaccharides and has potential applications in biotechnology. We used the metatranscriptomic technology to discover a thermophilic β-1,3-glucanase from compost. The phylogenetic study shows that it belongs to the family 16 glycoside hydrolase (GH16) and is most homologous with an enzyme from Streptomyces sioyaensis, an actinobacterium. It has the activity of 146.9 U/mg in the optimal reaction condition (75 °C and pH 5.5). Its catalytic domain was crystallized and diffracted to 1.14 Å resolution. The crystal structure shows a sandwich-like β-jelly-roll fold with two disulfide bonds. After analyzing the occurring frequencies of these cysteine residues, we designed two mutants (C160G and C180I) to study the role of these disulfide bonds. Both mutants have decreased their optimal temperature from 75 to 70 °C, which indicate that the disulfide bonds are important to maintain thermostability. Interestingly, the activity of C160G has increased ~ 17% to reach 171.4 U/mg. We speculate that the increased activity of C160G mutant is due to increased dynamics near the active site. Our studies give a good example of balancing the rigidity and flexibility for enzyme activity, which is helpful for protein engineering.

Composting of Olive Mill Pomace, Agro-Industrial Sewage Sludge and Other Residues: Process Monitoring and Agronomic Use of the Resulting Composts

The viability of co-composting of olive mill pomace added to sewage sludge with other organic residues was evaluated and the agronomic use of the final composts was investigated. Two composting piles at different carbon-nitrogen ratios were performed, in which olive mill pomace (OMP), sewage sludge from vegetable processing (SS), fresh residues from artichoke processing residues (AR), and wheat straw (WS) were used. The two composting piles were placed inside a specially built greenhouse and a turning machine pulled by a tractor was used for turning and shredding the organic matrix (every 6 days) during the process. The humidity and temperature of organic matrices have been monitored and controlled during the entire composting process, which lasted 90 days. The process was also monitored to evaluate the microbiological safety of the final compost. The humidity of both piles was always kept just above 50% until the end of the thermophilic phase and the maximum temperature was about 50 °C during the thermophilic phase. The carbon-nitrogen ratio decreased from 21.4 and 28.2, respectively (initial value at day 1 in Pile A and B), to values ranging from 12.9 to 15.1, both composts that originated from the two different piles were microbiologically safe. During a two-year period, the effects of different types of compost on the main qualitative parameters of processing tomato and durum wheat was evaluated. Five fertilization treatments were evaluated for tomato and durum wheat crops: unfertilized control (TR₁); compost A (TR₂); compost B (TR₃); ½ mineral and ½ compost A (TR₄); and mineral fertilizer commonly used for the two crops (TR₅). Concerning the processing tomato yield, TR₅ and TR₄ showed the best results (2.73 and 2.51 kg, respectively). The same trend was observed considering the marketable yield per plant. The only difference was related to the treatments that included the compost (2.32, 1.77, and 1.73 kg/plant for TR₄, TR₃, and TR₂, respectively). As regards the qualitative parameters of tomato, the highest average weight of the fruits was found in the TR₅, TR₄, and TR₃ treatments (respectively, 73.67 g, 70.34 g, and 68.10 g). For durum wheat, only the protein component was differentiated between treatments. Furthermore, wheat grain yield parameters generally increased by combined application of mineral fertilizer and compost.

Consumers’ and Farmers’ Perceptions in Europe Regarding the Use of Composted Bedding Material from Cattle

By-products like sawdust and straw are applied in compost bedded-pack barns (CBP) for cattle. These materials, which are gradually mixed with excreta and undergo a composting process, serve as a lying bed for the cattle. This study aims to assess the perception of consumers and farmers regarding the use of CBP during the grazing season of cattle for raising other animals or for growing food crops. This was examined by combining surveys with consumers from eight European countries and cattle farmers, focus groups with consumers, and in-depth interviews with individual farmers who implemented alternative uses of compost. The results showed that farmers preferred the compost bedded-pack system to the cubicle system in terms of sustainability and market aspects, although the cost of the bedding material required for CBP was seen as a significant negative aspect. Around half of all consumers indicated that the compost can be used for non-edible products and 26% indicated the compost can be used for raising other animals. Furthermore, 5% of consumers felt that compost should not be used for any other purpose. There were statistically significant differences between countries; therefore, regional specificities should be taken into account when marketing products from compost in CBP barns.

Factors Influencing the Persistence of Salmonella Infantis in Broiler Litter During Composting and Stabilization Processes and Following Soil Incorporation

Broiler litter (BL), a by-product of broiler meat production, is frequently contaminated with Salmonella and other zoonotic pathogens. To ensure the safety of crop production chains and limit pathogen spread in the environment, a pre-treatment is desired before further agricultural utilization. The objective of this study was to characterize the effect of physico-chemical properties on Salmonella persistence in BL during composting and stabilization and following soil incorporation, toward optimization of the inactivation process. Thirty-six combinations of temperature (30, 40, 50, and 60°C), water content (40, 55, and 70%; w/w), and initial pH (6, 7, and 8.5) were employed in static lab vessels to study the persistence of Salmonella enterica serovar Infantis (S. Infantis; a multidrug-resistant strain) during incubation of artificially-inoculated BL. The effect of aeration was investigated in a composting simulator, with controlled heating and flow conditions. Temperature was found to be the main factor significantly influencing Salmonella decay rates, while water content and initial pH had a secondary level of influence with significant effects mainly at 30 and 40°C. Controlled simulations showed faster decay of Salmonella under anaerobic conditions at mesophilic temperatures (&lt;45°C) and no effect of NH3 emissions. Re-wetting the BL at mesophilic temperatures resulted in Salmonella burst, and led to a higher tolerance of the pathogen at increased temperatures. Based on the decay rates measured under all temperature, water content, and pH conditions, it was estimated that the time required to achieve a 7 log10 reduction in Salmonella concentration, ranges between 13.7–27.2, 6.5–15.6, 1.2–4.7, and 1.3–1.5 days for 30, 40, 50, and 60°C, respectively. Inactivation of BL indigenous microbial population by autoclaving or addition of antibiotics to which the S. Infantis is resistant, resulted in augmentation of Salmonella multiplication. This suggests the presence of microbial antagonists in the BL, which inhibit the growth of the pathogen. Finally, Salmonella persisted over 90 days at 30°C in a Vertisol soil amended with inoculated BL, presumably due to reduced antagonistic activity compared to the BL alone. These findings are valuable for risk assessments and the formulation of guidelines for safe utilization of BL in agriculture.

Cascading effects of composts and cover crops on soil chemistry, bacterial communities and the survival of foodborne pathogens

AIMS

Recent foodborne disease outbreaks have caused farmers to re-evaluate their practices. In particular, concern that soil amendments could introduce foodborne pathogens onto farms and promote their survival in soils has led farmers to reduce or eliminate the application of animal-based composts. However, organic amendments (such as composts and cover crops) could bolster food safety by increasing soil microbial diversity and activity, which can act as competitors or antagonists and reduce pathogen survival.

METHODS AND RESULTS

Leveraging a study of a 27-year experiment comparing organic and conventional soil management, we evaluate the impacts of composted poultry litter and cover crops on soil chemistry, bacterial communities and survival of Salmonella enterica and Listeria monocytogenes. We found that bacterial community composition strongly affected pathogen survival in soils. Specifically, organic soils managed with cover crops and composts hosted more macronutrients and bacterial communities that were better able to suppress Salmonella and Listeria. For example, after incubating soils for 10 days at 20°C, soils without composts retained fourfold to fivefold more Salmonella compared to compost-amended soils. However, treatment effects dissipated as bacterial communities converged over the growing season.

CONCLUSIONS

Our results suggest that composts and cover crops may be used to build healthy soils without increasing foodborne pathogen survival.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our work suggests that animal-based composts do not promote pathogen survival and may even promote bacterial communities that suppress pathogens. Critically, proper composting techniques are known to reduce pathogen populations in biological soil amendments of animal origin, which can reduce the risks of introducing pathogens to farm fields in soil amendments. Thus, animal-based composts and cover crops may be a safe alternative to conventional fertilizers, both because of the known benefits of composts for soil health and because it may be possible to apply amendments in such a way that food-safety risks are mitigated rather than exacerbated.

Temporal and Agricultural Factors Influence Escherichia coli Survival in Soil and Transfer to Cucumbers

Biological soil amendments of animal origin (BSAAO) increase nutrient levels in soils to support the production of fruits and vegetables. BSAAOs may introduce or extend the survival of bacterial pathogens which can be transferred to fruits and vegetables to cause foodborne illness. Escherichia coli survival over 120 days in soil plots (3 m²) covered with (mulched) or without plastic mulch (not mulched), amended with either poultry litter, composted poultry litter, heat-treated poultry pellets, or chemical fertilizer, and transfer to cucumbers in 2 years (2018 and 2019) were evaluated. Plots were inoculated with E. coli (8.5 log CFU/m²) and planted with cucumber seedlings (Supremo). The number of days needed to reduce E. coli levels by 4 log CFU (dpi4log) was determined using a sigmoidal decline model. Random forest regression and one-way analysis of variance (ANOVA; P < 0.05) identified predictors (soil properties, nutrients, and weather factors) of dpi4log of E. coli and transfer to cucumbers. The combination of year, amendment, and mulch (25.0% increase in the mean square error [IncMSE]) and year (9.75% IncMSE) were the most prominent predictors of dpi4log and transfer to cucumbers, respectively. Nitrate levels at 30 days and soil moisture at 40 days were also impactful predictors of dpi4log. Differing rainfall amounts in 2018 (24.9 in.) and 2019 (12.6 in.) affected E. coli survival in soils and transfer to cucumbers. Salmonella spp. were recovered sporadically from various plots but were not recovered from cucumbers in either year. Greater transfer of E. coli to cucumbers was also shown to be partially dependent on dpi4log of E. coli in plots containing BSAAO.IMPORTANCE Poultry litter and other biological soil amendments are commonly used fertilizers in fruit and vegetable production and can introduce enteric pathogens such as Escherichia coli O157:H7 or Salmonella previously associated with outbreaks of illness linked to contaminated produce. E. coli survival duration in soils covered with plastic mulch or uncovered and containing poultry litter or heat-treated poultry litter pellets were evaluated. Nitrate levels on day 30 and moisture content in soils on day 40 on specific days were good predictors of E. coli survival in soils; however, the combination of year, amendment, and mulch type was a better predictor. Different cumulative rainfall totals from year to year most likely affected the transfer of E. coli from soils to cucumbers and survival durations in soil. E. coli survival in soils can be extended by the addition of several poultry litter-based soil amendments commonly used in organic production of fruits and vegetables and is highly dependent on temporal variation in rainfall.

A review on the valorisation of food waste as a nutrient source and soil amendment

Valorisation of food waste offers an economical and environmental opportunity, which can reduce the problems of its conventional disposal. Food waste is commonly disposed of in landfills or incinerated, causing many environmental, social, and economic issues. Large amounts of food waste are produced in the food supply chain of agriculture: production, post-harvest, distribution (transport), processing, and consumption. Food waste can be valorised into a range of products, including biofertilisers, bioplastics, biofuels, chemicals, and nutraceuticals. Conversion of food waste into these products can reduce the demand of fossil-derived products, which have historically contributed to large amounts of pollution. The variety of food chain suppliers offers a wide range of feedstocks that can be physically, chemically, or biologically altered to form an array of biofertilisers and soil amendments. Composting and anaerobic digestion are the main large-scale conversion methods used today to valorise food waste products to biofertilisers and soil amendments. However, emerging conversion methods such as dehydration, biochar production, and chemical hydrolysis have promising characteristics, which can be utilised in agriculture as well as for soil remediation. Valorising food waste into biofertilisers and soil amendments has great potential to combat land degradation in agricultural areas. Biofertilisers are rich in nutrients that can reduce the dependability of using conventional mineral fertilisers. Food waste products, unlike mineral fertilisers, can also be used as soil amendments to improve productivity. These characteristics of food wastes assist in the remediation of contaminated soils. This paper reviews the volume of food waste within the food chain and types of food waste feedstocks that can be valorised into various products, including the conversion methods. Unintended consequences of the utilisation of food waste as biofertilisers and soil-amendment products resulting from their relatively low concentrations of trace element nutrients and presence of potentially toxic elements are also evaluated.

A review of chemical and microbial contamination in food: What are the threats to a circular food system?

A circular food system is one in which food waste is processed to recover plant nutrients and returned to the soil to enable the production of more food, rather than being diverted to landfill or incineration. The approach may be used to reduce energy and water use in food production and contribute to the sustainability of the system. Anaerobic digestion and composting are common food waste treatment technologies used to stabilize waste and produce residual materials that can replenish the soil, thus contributing to a circular food system. This approach can only be deemed safe and feasible, however, if food waste is uncontaminated or any contaminants are destroyed during treatment. This review brings together information on several contaminant classes at different stages of the food supply chain, their possible sources, and their fates during composting and digestion. The main aim is to identify factors that could impede the transition towards a safe, reliable and efficient circular food system. We investigated heavy metals, halogenated organic compounds, foodborne pathogens and antibiotic resistance genes (ARGs) in the food system and their fates during digestion and composting. Production and processing stages were identified as major entry points for these classes of contaminants. Heavy metals and foodborne pathogens pose less risk in a circular system than halogenated organics or antibiotic resistance. Given the diversity of properties among halogenated organic compounds, there is conflicting evidence about their fate during treatment. There are relatively few studies on the fate of ARGs during treatment, and these have produced variable results, indicating a need for more research to clarify their fate in the final products. Repeated land application of contaminated food waste residuals can increase the risk of accumulation and jeopardize the safety of a circular food system. Thus, careful management of the system and research into the fate of the contaminants during treatment is needed.

Prevalence, Concentration, and Antimicrobial Resistance Profiles of Salmonella Isolated from Florida Poultry Litter

ABSTRACT

For over a decade, Salmonella contamination has increasingly led to outbreaks of foodborne illness associated with fresh produce. The use of untreated animal manures, or biological soil amendments of animal origin, to amend agricultural soils holds a risk of contamination from foodborne pathogens, such as Salmonella. This study was conducted to determine the prevalence, concentration, serotypes, and antimicrobial resistance profiles of Salmonella in poultry litter from Florida farms. Litter pH, total Kjeldahl nitrogen, total ammonia nitrogen, total phosphorus (P2O5), total potassium (K2O), moisture content, total solids, total ash, organic matter, and aerobic plate count (APC) were also measured. Litter samples (n = 54) were collected from 18 broiler farms across three seasons (spring, summer, and winter). Salmonella concentrations were enumerated using a most-probable-number (MPN) method, and antimicrobial susceptibility testing was performed. The prevalence of Salmonella in litter samples was 61.1%, with a geometric mean of 0.21 ± 20.7 MPN/g. Across all seasons, Salmonella concentrations were not influenced by the chemical, physical, or microbial properties measured. Recovered Salmonella isolates (n = 290) were grouped into serogroups O:4 (43.1%), O:7 (26.9%), O:8 (11.0%), O:1,3,10,19 (7.9%), and O:9,46 (7.2%). Serotyping Salmonella isolates (n = 47) resulted in 12 serotypes, with the most common being Typhimurium (27.7%), Kentucky (17.0%), Enteritidis (14.9%), and Mbandaka (14.9%). Antimicrobial resistance to tetracycline (29.8%), sulfisoxazole (23.4%), and streptomycin (14.9%) was observed. No isolates were resistant to more than two antimicrobial agents. This study provides valuable information for future risk assessments for the use of poultry litter as an untreated biological soil amendment of animal origin.

HIGHLIGHTS

Induction of Escherichia coli O157:H7 into a viable but non-culturable state by high temperature and its resuscitation

Escherichia coli O157:H7, a causative agent of haemolytic uremic syndrome, can enter into a viable but non-culturable (VBNC) state in response to harsh stress. Bacteria in this state can retain membrane integrity, metabolic activity and virulence expression, which may present health risks. However, virulence expression and resuscitation ability of the VBNC state are not well understood. Here, we induced E. coli O157:H7 into a VBNC state by high temperature, which is commonly used to prevent the proliferation of pathogens in process of soil solarization, composting and anaerobic digestion of organic wastes. The virulence genes were highly expressed in the VBNC state and resuscitated daughter cells. The resuscitation of VBNC cells occurred after the removal of heat stress in Luria-Bertani medium. In addition, E. coli O157: H7 cells can leave the VBNC state and resuscitate with the clearance of protein aggregates. Notably, with the accumulation of protein aggregation and increased levels of reactive oxygen species, cells lost their ability to resuscitate. The results of this study not only can facilitate a better understanding of the health risks associated with the VBNC state but also have the potential to provide a theoretical basis for thermal disinfection processing.

Composting of toxic weed Parthenium hysterophorus: Nutrient changes, the fate of faecal coliforms, and biopesticide property assessment

This study aimed to investigate; composting of toxic weed Parthenium with cow dung in (2:1, and 1:1 ratio); and the changes in Escherichia coli and Salmonella population; as well as the antimicrobial property of ready compost. Organic carbon decreased by 45-52% while total nitrogen, total potassium, available phosphorus increased by 1.87- to 3.21-, 1.65- to 1.83-, and 4.03- to 3.33-folds, respectively in Parthenium setups. Germination index value (110-132%) indicates no phytotoxicity of composted Parthenium. E. coli reduced by 6.87 to 6.90 log population (<1000 CFU g^-1, safe limit) while Salmonella was in non-detectable limit in compost samples. Results of the antimicrobial test indicate a strong biocidal activity by non-sterilized compost extract against plant pathogens Xanthomonas citrus, Xanthomonas campestris, and Erwinia carotovora. Xanthomonas spp. It is concluded that thermophilic composting could convert Parthenium into a product with biomanure and biopesticide property for sustainable agriculture production.

Effect of soil type and temperature on survival of Salmonella enterica in poultry manure-amended soils

The effects of soil type and temperature on the survival of a cocktail of five Salmonella enterica serotypes (Enteritidis, Infantis, Montevideo, Typhimurium and Zanzibar) in manure-amended soils under controlled laboratory conditions was assessed. Containers of clay loam or sandy soil, unaltered or amended with 2% (w/w) poultry manure, were inoculated with S. enterica (~5 log₁₀ CFU per gram) and held at 5, 21 or 37°C for 6 weeks. Statistical analysis of the persistence of S. enterica identified a significant three-way interaction between soil type, manure amendment and temperature. Clay loam soils and lower temperatures tended to support S. enterica persistence over 6 weeks with only 1- and 2-log reductions respectively. In contrast, sand and higher temperatures resulted in a 4-log and either 3- to 4-log reductions respectively. Manure amendment had an overarching effect of reducing die-off of S. enterica in comparison with unamended soils. This study highlights that a large component of variation of the rate of S. enterica reduction in soils may be attributed to combinations of environmental factors, in particular, soil type and temperature. It further underscores the importance of risk management strategies and industry guidelines based on local data and that reflect the diversity of prevailing horticultural production environments. SIGNIFICANCE AND IMPACT OF THE STUDY: The persistence of Salmonella enterica in soil environments was shown to be significantly influenced by a range of individual and interacting environmental effects, including temperature, soil type and amendment addition. This indicates that current horticultural food safety management systems which employ a uniform prescribed exclusion period between application of manure and time of harvest may be unfit for purpose under certain conditions by either underestimating or overestimating pathogen die-off. These findings support exclusion periods that account for a range of environmental factors including temperature, soil type and growing region that may be more appropriate to manage microbiological risks associated with soil which has been amended with manure.

Collection of ear corn residue and its utilization as a bulking agent for cow manure composting

This study examined the collection, storage, and utilization of ear corn residue as a bulking agent for composting. Ear corn residue left in fields was collected by a sequence of windrowing and round baling operations, which showed a collection efficiency of 53%-56%. More than 70% of the corn stalks had lengths shorter than 15 cm. The moisture content of corn residue collected in late October was approximately 58%; it decreased to 23% during storage. Dried corn residue was mixed with raw manure in two different ways, namely using complete mixing (CM) treatment or creating a bottom layer of residue, and a total of 3.4 t of the manure and ear corn residue mixture were composted using a pilot-scale composting apparatus. The results showed that the CM treatment resulted in higher temperature generation and produced less odorous and well-degraded compost after 2 months of composting, while the odorous compounds in the compost with corn residue as the bottom layer remained similar to those of the initial compost. To sufficiently utilize the advantages of the ear corn residue, thorough mixing of the corn residue with raw manure is preferable; this procedure produced well-degraded and safety compost in a shorter time period.