Microbial Reactions Research Articles

Microbial | electrochemical CO2 reduction: To integrate or not to integrate?

Microbial | electrochemical CO2 reduction: To integrate or not to integrate?

Physiological Acclimation Extrapolates the Kinetics and Thermodynamics of Methanogenesis From Laboratory Experiments to Natural Environments

Chemotrophic microorganisms face the steep challenge of limited energy resources in natural environments. This observation has important implications for interpreting and modeling the kinetics and thermodynamics of microbial reactions. Current modeling frameworks treat microbes as autocatalysts, and simulate microbial energy conservation and growth with fixed kinetic and thermodynamic parameters. However, microbes are capable of acclimating to the environment and modulating their parameters in order to gain competitive fitness. Here we constructed an optimization model and described microbes as self-adapting catalysts by linking microbial parameters to intracellular metabolic resources. From the optimization results, we related microbial parameters to the substrate concentration and the energy available in the environment, and simplified the relationship between the kinetics and the thermodynamics of microbial reactions. We took as examplesMethanosarcinaandMethanosaeta– the methanogens that produce methane from acetate – and showed how the acclimation model extrapolated laboratory observations to natural environments and improved the simulation of methanogenesis and the dominance ofMethanosaetaoverMethanosarcinain lake sediments. These results highlight the importance of physiological acclimation in shaping the kinetics and thermodynamics of microbial reactions and in determining the outcome of microbial interactions.

Spatiotemporal variations of redox conditions and microbial responses in a typical river bank filtration system with high Fe2+ and Mn2+ contents

The redox conditions strongly affect redox kinetics, hydrochemical composition and microbial reactions under river bank filtration (RBF). For investigating the redox conditions, zonation factors, and microbial responses in a typical RBF with high Fe2+ and Mn2+ contents, three wells were established 20 m apart perpendicular to the south bank of the Songhua River with a constant flow rate of 400 m3/h. Redox zonation was identified from the redox sequences, redox products, reactions identified and seasonality. High-throughput sequencing, principal coordinates analysis, and redundancy analysis were used to identify the microbial responses to redox zonation. The results indicated that the RBF was stabilized after 21 d of water extraction with a 51%, 36% and 21% decrease of Fe2+, Mn2+ and NH4+ contents, respectively. Feature redox indices varied with strong regularity in the horizontal and vertical filtration directions, and the filtration area could be divided into O2/NO3−, Fe/Mn, and SO42− reduction zones. Seasonality resulted in markedly fluctuation of Fe2+ and Mn2+ contents in groundwater. Pseudomonas, Flavobacterium, and Limnobacter were the dominant bacteria in the O2/NO3−, Fe/Mn, and SO42− reduction zones, respectively. DO explained 21.1% of microbial variability in the fluctuation zone, while Mn2+ and Fe2+ explained 27.7%, and 26.2%, respectively, of microbial variability in the saturated zone.

Anthraquinone-2-Sulfonate as a Microbial Photosensitizer and Capacitor Drives Solar-to-N2O Production with a Quantum Efficiency of Almost Unity.

Semiartificial photosynthesis shows great potential in solar energy conversion and environmental application. However, the rate-limiting step of photoelectron transfer at the biomaterial interface results in an unsatisfactory quantum yield (QY, typically lower than 3%). Here, an anthraquinone molecule, which has dual roles of microbial photosensitizer and capacitor, was demonstrated to negotiate the interface photoelectron transfer via decoupling the photochemical reaction with a microbial dark reaction. In a model system, anthraquinone-2-sulfonate (AQS)-photosensitized Thiobacillus denitrificans, a maximum QY of solar-to-nitrous oxide (N2O) of 96.2% was achieved, which is the highest among the semiartificial photosynthesis systems. Moreover, the conversion of nitrate into N2O was almost 100%, indicating the excellent selectivity in nitrate reduction. The capacitive property of AQS resulted in 82-89% of photoelectrons released at dark and enhanced 5.6-9.4 times the conversion of solar-to-N2O. Kinetics investigation revealed a zero-order- and first-order- reaction kinetics of N2O production in the dark (reductive AQS-mediated electron transfer) and under light (direct photoelectron transfer), respectively. This work is the first study to demonstrate the role of AQS in photosensitizing a microorganism and provides a simple and highly selective approach to produce N2O from nitrate-polluted wastewater and a strategy for the efficient conversion of solar-to-chemical by a semiartificial photosynthesis system.

Identification of a fungal cytochrome P450 with steroid two-step ordered selective hydroxylation characteristics in Colletotrichum lini

Microbial hydroxylation reaction has greatly enriched the number of steroids and created many meaningful new compounds. The dihydroxylation of dehydroepiandrosterone (DHEA) by filamentous fungi produces an important product 3β,7α,15α-trihydroxy-5-androstene-17-one (7α,15α-diOH-DHEA), which can be used as a key intermediate for the synthesis of contraceptive drospirenone. The introduction of microbial hydroxylation reaction reduces the traditional chemical synthesis process by 4 steps and greatly improves the productivity and economic efficiency. Colletotrichum lini is an industrial strain producing 7α,15α-diOH-DHEA, but the related cytochrome P450 that plays hydroxylation effect has not yet been discovered. In this work, a combination of quantitative proteomics, qRT-PCR, and functional expression in Pichia pastoris was used to identify highly induced steroid hydroxylase from Colletotrichum lini ST-1. A novel fungal cytochrome P450 monooxygenase CYP68JX was identified. The biotransformation in recombinant yeast confirmed that the cytochrome P450 has steroid C7α and C15α hydroxylase activities. The hydroxylation of DHEA by CYP68JX is an ordered reaction, proceeding from the C7 to the C15 site of the steroidal nucleus. The cloning and identification of the CYP68JX gene provide useful information for deepening the understanding regarding the structural basis of its regional and stereoselectivity.

Applying the Soil Management Assessment Framework (SMAF) to Assess Mangrove Soil Quality

Soil quality (SQ) refers to its capacity to perform its functions. Thus, the SQ index (SQI) is a potentially useful tool for monitoring soil changes induced by mangrove restoration initiatives. Although the soil management assessment framework (SMAF) is a well-developed tool for SQ assessments in diverse ecosystems, it has never been tested on mangrove soils. In this study, we tested the SMAF to evaluate the shifts in the SQ of mangroves in a reforestation initiative using three- and seven-year plantations, which were compared with degraded and mature mangroves. A minimum dataset, composed of the pH and available P as chemical indicators, bulk density as a physical indicator, and soil organic carbon as a biological indicator, was used to calculate the SQI. The SMAF scores facilitated the monitoring of improvement in the mangrove SQ with vegetation development, mainly driven by physical and biological indicators. The SMAF may be a useful tool for monitoring SQ in mangroves under protection and recovery initiatives. Nevertheless, we suggest the inclusion of additional biological and chemical indicators in the minimum dataset for future studies to better represent specific processes and functions (e.g., microbial redox reactions and contaminant immobilization) that can alter the SQ of mangroves.

Effects of organic carbon and sulfide on the anammox reaction in the anoxic column in the SRDAPN process for treating high-strength wastewater

Low energy consumption treatment of high-strength wastewater is crucial in controlling groundwater pollution and eutrophication in closed waterbodies. In this study, the sulfate reduction, denitrification/anammox, and partial nitrification (SRDAPN) process, which is an effective organic carbon and nitrogen removal process with low energy consumption for low strength wastewater, was applied to treat livestock wastewater with high COD and sulfate concentration, and microbial reaction and community were examined using an anaerobic–anoxic biological filter reactor that simulates circulation from an aerobic reactor. At a total organic carbon loading rate of 2.7–5.8 kgC/m3·day, sulfate reduction and methane production occurred simultaneously in the anaerobic column of the reactor. Specifically, sulfate reduction resulted in organic matter removal rates of 38 and 26% at ambient temperature and 25 °C, respectively. Furthermore, both heterotrophic and autotrophic denitrification occurred in the anoxic column, and when the organic loading rate in the anoxic reactor was below 0.2 kgC/m3·day, 33%–37% of ammonium and 33%–34% of nitrite were removed by the anammox reaction. Heterotrophic denitrification bacteria (Thauera, Comamonas, and Denitratisoma) and sulfur denitrification bacteria (Sulfurimonas denitrificans) grew in the lower and middle parts of the anoxic column, whereas anammox bacteria (2.5% of Candidatus Brocadia at ambient temperature and 9.4% of Candidatus Kuenenia at 25 °C) grew in the upper part of the anoxic column. These results indicate that the SRDAPN process based on sulfur cycle and anammox is useful for treatment of high strength wastewater with low energy consumption.

Review on Research Progress of MICP Technology

MICP technology is a new technology proposed for soil reinforcement research in recent years, which has the advantages of environmental protection and sustainability. Through the review and analysis of domestic and foreign literature, the mechanism of microbial mineralization reaction and the research progress of domestic and foreign scholars were comprehensively summarized. This paper introduces the basic principle of urea hydrolysis in MICP technology, and expounds the control factors of microbial mineralization experiment and the practical application of this technology in engineering. Finally, the future development prospect of MICP technology is forecasted.

Global genomic analysis of microbial biotransformation of arsenic highlights the importance of arsenic methylation in environmental and human microbiomes

Arsenic is a ubiquitous toxic element, the global cycle of which is highly affected by microbial redox reactions and assimilation into organoarsenic compounds through sequential methylation reactions. While microbial biotransformation of arsenic has been studied for decades, the past years have seen the discovery of multiple new genes related to arsenic metabolism. Still, most studies focus on a small set of key genes or a small set of cultured microorganisms. Here, we leveraged the recently greatly expanded availability of microbial genomes of diverse organisms from lineages lacking cultivated representatives, including those reconstructed from metagenomes, to investigate genetic repertoires of taxonomic and environmental controls on arsenic metabolic capacities. Based on the collection of arsenic-related genes, we identified thirteen distinct metabolic guilds, four of which combine the aio and ars operons. We found that the best studied phyla have very different combinations of capacities than less well-studied phyla, including phyla lacking isolated representatives. We identified a distinct arsenic gene signature in the microbiomes of humans exposed or likely exposed to drinking water contaminated by arsenic and that arsenic methylation is important in soil and in human microbiomes. Thus, the microbiomes of humans exposed to arsenic have the potential to exacerbate arsenic toxicity. Finally, we show that machine learning can predict bacterial arsenic metabolism capacities based on their taxonomy and the environment from which they were sampled.

A review on bio-electro-Fenton systems as environmentally friendly methods for degradation of environmental organic pollutants in wastewater.

Bio-electro-Fenton (BEF) systems have been potentially studied as a promising technology to achieve environmental organic pollutants degradation and bioelectricity generation. The BEF systems are interesting and constantly expanding fields of science and technology. These emerging technologies, coupled with anodic microbial metabolisms and electrochemical Fenton's reactions, are considered suitable alternatives. Recently, great attention has been paid to BEFs due to special features such as hydrogen peroxide generation, energy saving, high efficiency and energy production, that these features make BEFs outstanding compared with the existing technologies. Despite the advantages of this technology, there are still problems to consider including low production of current density, chemical requirement for pH adjustment, iron sludge formation due to the addition of iron catalysts and costly materials used. This review has described the general features of BEF system, and introduced some operational parameters affecting the performance of BEF system. In addition, the results of published researches about the degradation of persistent organic pollutants and real wastewaters treatment in BEF system are presented. Some challenges and possible future prospects such as suitable methods for improving current generation, selection of electrode materials, and methods for reducing iron residues and application over a wide pH range are also given. Thus, the present review mainly revealed that BEF system is an environmental friendly technology for integrated wastewater treatment and clean energy production.

Online Glucose Analysis System With High Precision and Wide Detection Range for Fermentation Monitoring

Online glucose monitoring during the fermentation process is critical for evaluating the microbial metabolism state and reaction course, achieving precise process control for industrial efficiency enhancement. However, the fast, wide-range and highly accurate test technique always presents a challenge for state-of-the-art analytical instruments. In this work, we proposed an online glucose analysis system based on a homemade screen-printed enzymatic biosensor chip composed of Prussian blue nanocubes with a high sensitivity of 83.404 mA mM <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . To match the detection behavior of this chip, a specific signal conversion system was designed to realize the highly precise acquisition and treatment of nA-level currents by integrating hardware acquisition circuits and Kalman filtering algorithms. Focusing on the continuous change in glucose concentration during fermentation, an adaptive injection strategy for the sampling volume was proposed to achieve an ultrawide linear range from 1 g/L to 180 g/L. The results show that the online analytical system exhibits excellent detection performance with high accuracy and low relative error of detection (<2%) during the fermentation of sophorolipid and ethanol compared to high performance liquid chromatography and commercial analyzers.

PH-Based Control Strategies for the Nitrification of High-Ammonium Wastewaters

Aquatic nitrogen pollution is one of the most urgent environmental issues requiring prevention and mitigation. Large quantities of high-ammonium wastewaters are generated by several industrial sectors, such as fertilizer and anaerobic-digestion plants. Nitrification of these wastewaters is commonly carried out, either to remove nitrogen or produce liquid fertilizers. Standard control methodologies for the efficient nitrification of high-ammonium wastewaters to produce liquid fertilizers have not yet been established and are still within their early stages of development. In this paper, novel pH-based control algorithms are presented that maintain operation at the microbial maximum reaction rate (υmax) in batch and continuous reactors. Complete conversion of ammonium to nitrate was achieved in a batch setup, and a conversion of 93% (±1%) was achieved in a continuously-stirred-tank-reactor. The unparalleled performance and affordability of the control schemes proposed offer a steppingstone to the future of sustainable fertilizer production.

Activation of extracellular electron network in non-electroactive bacteria by Bombyx mori silk

Extracellular electron transfer material (EETM) has increasingly attracted attentions for the enhancing effect on multiple microbial reactions. Especially, EETM is known to be essential to activate the energy network in non-electroactive bacteria. It is motivated to find out an EETM which is natural-based, environmentally friendly, and easily produced at large-scale. In this study, Bombyx mori silk is found, for the first time, to function as an EETM by using an EETM-dependent pentachlorophenol (PCP) dechlorinating anaerobic microbial culture. Subsequently, by dividing fibroin fiber into different soluble/insoluble fractions and correlating their EET functions with their structural properties based on various spectroscopic analyses, the β-sheet configuration is suggested as an essential structure supporting the EET function of silk materials. The analyses also suggested the involvement of sulfur-containing amino acids in this function. The EET function is not degraded by boiling or acid/alkaline treatments and the material can be utilized multiple times, although it is susceptible to UV irradiation. Bombyx mori silk also enhance other microbial reactions, including Fe(III)OOH reduction, CO2 reduction to acetate, and nitrogen fixation. This discovery provides a basis for developing biotechnology for environmental remediation, global warming reduction, and biofertilizer production using Bombyx mori silk and its wastes.

Extreme biogeochemical effects following simulation of recurrent drought in acid sulfate soils

Droughts are increasing in frequency and severity in many regions of the world and there are uncertainties how recurrent drought will impact acid sulfate soils, which can undergo extreme and persistent acidification (pH < 4) following oxidation. Using column experiments, we induced a 9 week drought/drying and 9 week rewetting phase in two acid sulfate soil profiles with sulfuric (pH < 4) and hypersulfidic materials from the Lower River Murray region of Australia's largest river system. These soils had not yet recovered from the extreme period of the ‘Millennium Drought’ between 2007 and 2010. pH, redox potential, dissolved metals and greenhouse gases (CO2, CH4 and N2O) were measured at multiple depths in each column every 3 weeks during the drying and rewetting phases. The solid phase of the Sulfuric and Hypersulfidic clay soil profiles in both column experiments were analysed for complete acid-base accounting (actual and retained acidity, potential acidity in the form of pyrite, and acid neutralising capacity) and reactive metals at the beginning and end of the experiment. Residual pyrite, present in high concentrations in the Sulfuric clay soil column, oxidised during the drying period, further lowering the pH (<4) and mobilising dissolved metals (Al, Cd, Cu, Ni, Zn). More reactive Fe and Al phases were formed during the drying-rewetting cycle while reactive Mn decreased. The soil pH did not recover (i.e. increase) during the rewetting phase in both the Sulfuric and Hypersulfidic clay soils, likely due to barriers to microbial reduction reactions, although Fe-oxidising bacteria were likely still active as CO2 was released. Acid sulfate soils may not recover in inter-drought periods and more severe impacts can be expected following recurrent droughts.

Bioactive Edible Films and Coatings Based in Gums and Starch: Phenolic Enrichment and Foods Application

Edible films and coatings allow preserving fresh and processed food, maintaining quality, preventing microbial contamination and/or oxidation reactions and increasing the shelf life of food products. The structural matrix of edible films and coatings is mainly constituted by proteins, lipids or polysaccharides. However, it is possible to increase the bioactive potential of these polymeric matrices by adding phenolic compounds obtained from plant extracts. Phenolic compounds are known to possess several biological properties such as antioxidant and antimicrobial properties. Incorporating phenolic compounds enriched plant extracts in edible films and coatings contribute to preventing food spoilage/deterioration and the extension of shelf life. This review is focused on edible films and coatings based on gums and starch. Special attention is given to bioactive edible films and coatings incorporating plant extracts enriched in phenolic compounds.

Crystallization Behavior and Quality of Frozen Meat.

Preservation of meat through freezing entails the use of low temperatures to extend a product’s shelf-life, mainly by reducing the rate of microbial spoilage and deterioration reactions. Characteristics of meat that are important to be preserve include tenderness, water holding capacity, color, and flavor. In general, freezing improves meat tenderness, but negatively impacts other quality attributes. The extent to which these attributes are affected depends on the ice crystalline size and distribution, which itself is governed by freezing rate and storage temperature and duration. Although novel technology has made it possible to mitigate the negative effects of freezing, the complex nature of muscle tissue makes it difficult to accurately and consistently predict outcome of meat quality following freezing. This review provides an overview of the current understanding of energy and heat transfer during freezing and its effect on meat quality. Furthermore, the review provides an overview of the current novel technologies utilized to improve the freezing process.

Microbiome characteristics and the key biochemical reactions identified on stone world cultural heritage under different climate conditions

The surfaces of historical stone monuments are visibly covered with a layer of colonizing microorganisms and their degradation products. In this study, a metadata analysis was conducted using the microbial sequencing data available from NCBI database to determine the diversity, biodeterioration potential and functionality of the stone microbiome on important world cultural heritage sites under four different climatic conditions. The retrieved stone microbial community composition in these metagenomes shows a clear association between climate types of the historical monuments and the diversity and taxonomic composition of the stone microbiomes. Shannon diversity values showed that microbial communities on stone monuments exposed to dry climate were more diverse than those under humid ones. In particular, functions associated with photosynthesis and UV resistance were identified from geographical locations under different climate types. The distribution of key microbial determinants responsible for stone deterioration was linked to survival under extreme environmental conditions and biochemical capabilities and reactions. Among them, biochemical reactions of the microbial nitrogen and sulfur cycles were most predominant. These stone-dwelling microbiomes on historical stone monuments were highly diverse and self-sustaining driven by energy metabolism and biomass accumulation. And metabolic products of the internal geomicrobiological nitrogen cycling on these ancient monuments play a unique role in the biodeterioration of stone monuments. These results highlight the significance of identifying the essential microbial biochemical reactions to advance the understanding of stone biodeterioration for protection management.

Efficacy and safety of polymyxin B in carbapenem-resistant gram-negative organisms infections

ObjectiveTo investigate how to use polymyxin B rationally in order to produce the best efficacy and safety in patients with carbapenem-resistant gram-negative organisms (CRO) infection.MethodsThe clinical characteristics and microbiological results of 181 patients caused by CRO infection treated with polymyxin B in the First Affiliated Hospital from July 2018 to May 2020 were retrospectively analyzed. The bacterial clearance rate, clinical efficacy, adverse drug reactions and 28 days mortality were evaluated.ResultsThe overall effective rate of 181 patients was 49.72%, the total bacterial clearance rate was 42.0%, and the 28 day all-cause mortality rate was 59.1%. The effective rate and bacterial clearance rate in the group of less than 24 h from the isolation of CRO to the use of polymyxin B were significantly higher than those in the group of more than 24 h. Logistics multivariate regression analysis showed that the predictive factors for effective treatment of CRO with polymyxin B were APACHEII score, duration of polymyxin B treatment, combination of polymyxin B and other antibiotics, and bacterial clearance. 17 cases (9.36%) of acute kidney injury were considered as polymyxin B nephrotoxicity and 4 cases (23.5%) recovered after polymyxin B withdrawal. After 14 days of polymyxin B use, 3 cases of polymyxin B resistance appeared, and there were 2 cases of polymyxin B resistance in the daily dose 1.5 mg/kg/day group.ConclusionFor CRO infection, the treatment of polymyxin B should be early, combined, optimal dose and duration of treatment, which can achieve better clinical efficacy and microbial reactions, and reduce the adverse reactions and drug resistance.

Chemistry and microbiology in sugar extraction

The stability of the sucrose molecule and the firmness of the tissue structure in the cossettes are of major concern when optimizing the operating conditions for the extraction system. For a given extraction system the retention time is more or less fixed, but the actual pH values and temperatures to be set across the system largely determine the extent to which both sugar gets lost by hydrolysis and the cossette structure deteriorates, particularly by dissolution of pectin. Furthermore, potential sugar loss by microbial infection in the extraction system needs to be controlled too. The influence of the pH value and temperature on these undesirable chemical and microbial reactions will be outlined in this paper, including the consequences for the subsequent processing steps. It can be concluded that the recommended optimal pH values and temperatures for operating the extraction system are a compromise between good and bad.

Comparable Expressions of Bacillus species on Different Growth Media

Abstract: An investigation was carried out using Pikovskaya Broth (PKB), Luria Bertani Broth (LBB), and Peptone Water (PW) to analyse growth expressions of constructed Bacillus subtilis sub sp and compared to a commercial Bacillus subtilis RIK 1285. The aim was to determine the effect of carbon, nitrogen and other elements at different variations on the metabolic activities under different conditions. The results obtained showed growth density of 4.1 g/ml at 70oC and 3.1 g/ml at pH 6.0; 3.3 g/ml at 70oC and 2.8 g/ml at pH 6.0; 3.8 g/ml at 60oC and 2.6 g/ml at pH 7.0 from PKB, LBB and PW respectively. The growth density of the commercial strain recorded 3.8 g/ml at 50oC and 2.8 g/ml at pH 7.0; 3.1 g/ml at 50oC and 2.3 g/ml; 3.0 at 50oC and 2.3 at pH respectively. The investigation showed importance and relevance of gene metabolic upgrade on the utilization of multiple nutrients present from one media to another. Keywords: media formulation, microbial reaction, growth promoters, growth density