Effect of nitroethane and nitroethanol on the production of indole and 3-methylindole (skatole) from bacteria in swine feces by gas chromatography

Visible-light-driven photo-peroxidase catalysis: high-efficiency degradation of indole in water

The demand for H2O2 restricts the wider application of horseradish peroxidase (HRP) in degradation. In this work, a novel photoenzyme synergistic catalytic system was developed for high-efficiency degrading of indole in water by HRP without extra H2O2. The HRP was immobilized on CN-ZIF prepared by the combination of g-C3N4 and ZIF-8 to achieve photo-peroxidase catalyst HRP/Zn-CN-ZIF. Under visible light, photogenerated electrons and H2O2 from HRP/Zn-CN-ZIF participated in the biocatalytic cycle of HRP directly. As a result, the indole at 20 mg L-1 in water was degraded completely in 2 h by the HRP/Zn-CN-ZIF photoenzyme synergistic catalytic system without the addition of H2O2. Furthermore, HRP/Zn-CN-ZIF exhibited superior visible light absorption and charge transfer ability compared to g-C3N4. The results of the mechanism studies suggest that ·OH would play the most significant role from the HRP/Zn-CN-ZIF in indole degradation. This research provides an efficient approach for the removal of indole from water environments.

Innovative Treatments Enhancing the Functionality of Gut Microbiota to Improve Quality and Microbiological Safety of Foods of Animal Origin

The gastrointestinal tract, or gut, microbiota is a microbial community containing a variety of microorganisms colonizing throughout the gut that plays a crucial role in animal health, growth performance, and welfare. The gut microbiota is closely associated with the quality and microbiological safety of foods and food products originating from animals. The gut microbiota of the host can be modulated and enhanced in ways that improve the quality and safety of foods of animal origin. Probiotics—also known as direct-fed microbials—competitive exclusion cultures, prebiotics, and synbiotics have been utilized to achieve this goal. Reducing foodborne pathogen colonization in the gut prior to slaughter and enhancing the chemical, nutritional, or sensory characteristics of foods (e.g., meat, milk, and eggs) are two of many positive outcomes derived from the use of these competitive enhancement–based treatments in food-producing animals.

Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Roles of Nitrocompounds in Inhibition of Foodborne Bacteria, Parasites, and Methane Production in Economic Animals

Simple Summary

Supplementation of nitrocompounds in animal diets has been studied to investigate their effects on economic animals. It has been known that nitrocompounds are capable of inhibiting pathogens, parasites, methane and ammonia production. The toxicity, metabolism, and mechanisms of actions have been discussed in the review to conclude the advantages and disadvantages of application of nitrocompounds in animal production.

Abstract

Nitrocompounds are derivatives of hydrocarbons, alcohols, fatty acids, and esters, consisting one or more nitro functional groups. Either natural sources of nitrocompounds or synthetic chemicals have been applied in animal diets to investigate their effects on economic animals, since conjugates of 3-nitropropanol and 3-nitropropionic acid were isolated from Astragalus oblongifolius. In this review, emphasis will be placed on nitrocompounds’ antimicrobial activity, toxicity, metabolisms and mechanisms of actions. Nitrocompounds can be metabolized by ruminal microbials, such as Denitrobacterium detoxificans, or alcohol dehydrogenase in the liver. Moreover, it has been found that nitrocompounds are capable of inhibiting pathogens, parasites, methane and ammonia production; however, overdose of nitrocompounds could cause methemoglobinemia or interfere with energy production in mitochondria by inhibiting succinate dehydrogenase.

Aerobic biotransformation of 3-methylindole to ring cleavage products by Cupriavidus sp. strain KK10

3-Methylindole, also referred to as skatole, is a pollutant of environmental concern due to its persistence, mobility and potential health impacts. Petroleum refining, intensive livestock production and application of biosolids to agricultural lands result in releases of 3-methylindole to the environment. Even so, little is known about the aerobic biodegradation of 3-methylindole and comprehensive biotransformation pathways have not been established. Using glycerol as feedstock, the soil bacterium Cupriavidus sp. strain KK10 biodegraded 100 mg/L of 3-methylindole in 24 h. Cometabolic 3-methylindole biodegradation was confirmed by the identification of biotransformation products through liquid chromatography electrospray ionization tandem mass spectrometry analyses. In all, 14 3-methylindole biotransformation products were identified which revealed that biotransformation occurred through different pathways that included carbocyclic aromatic ring-fission of 3-methylindole to single-ring pyrrole carboxylic acids. This work provides first comprehensive evidence for the aerobic biotransformation mechanisms of 3-methylindole by a soil bacterium and expands our understanding of the biodegradative capabilities of members of the genus Cupriavidus towards heteroaromatic pollutants.

Skatole remediation potential of Rhodopseudomonas palustris WKU-KDNS3 isolated from an animal waste lagoon

Skatole (3MI) is a major contributor to the malodor emission resulting from ruminant and human faeces. The remediation of malodor has been a major challenge for the animal production industry. In this investigation, a pure culture of purple nonsulphur bacterium capable of degrading 3MI was isolated from a swine waste lagoon using an enrichment technique and identified as Rhodopseudomonas palustris WKU-KDNS3 based on 16S rRNA analysis and UV-visible spectroscopy. The cell structure of the organism was confirmed by transmission electron microscopy. Growth profile and 3MI removal pattern were determined using media supplemented with 0.1 μmol 3MI under short-term and long-term aerobic growth conditions. The organism grew on 3MI media as luxuriantly as control (without 3MI). Growth of R. palustris WKU-KDNS3 demonstrated a significant reduction in the level of 3MI (>48%) in 72 h. The level of 3MI dropped further by >93% of the total concentration present in the medium in 21 days. Skatole remediation potential of R. palustris WKU-KDNS3 can be judiciously utilized in various animal and industrial waste treatment systems.

SIGNIFICANCE AND IMPACT OF THE STUDY

Odour pollution is a serious environmental problem, particularly in the agriculture industry, and technologies based on chemical remediation are less effective and cost prohibitive. In this study, the newly isolated Rhodopseudomonas palustris strain WKU-KDNS3 causes biodegradation of 3-methylindole (skatole), which is one of the most offensive odorants present in wastewater lagoons. Aerobic degradation of this widely spread aromatic pollutant by Rhodopseudomonas strain is a significant finding that enhances the present understanding about metabolic versatility of purple photosynthetic nonsulphur bacteria. The remediation potential of R. palustris WKU-KDNS3 can also be gainfully utilized in various waste treatment facilities.