Acceleration of lactate-utilizing pathway for enhancing biohydrogen production by magnetite supplementation in Clostridium butyricum.

A conductive metal compound can be used as a catalyst for enhancing hydrogen production by dark fermentation. This study aimed to identify mechanisms of enhanced hydrogen production by magnetite supplementation. Experiments were performed with lactate and/or magnetite supplementation to confirm that the lactate-utilizing pathway is the key cause of enhanced hydrogen production. Also, ribonucleic acid sample was collected for monitoring gene regulation under each condition. Hydrogen production was significantly enhanced by approximately 25.6% and 58.9%, respectively, via magnetite alone and with lactate. Moreover, the expression of genes involved in hydrogen production, including pyruvate ferredoxin oxidoreductase, hydrogenase, and ferredoxin, via magnetite alone and with lactate was upregulated by 0.26, 0.71, and 3.50 and 1.06, 2.14, and 1.94 times, respectively.

A critical review on microbes-based treatment strategies for mitigation of toxic pollutants.

Contamination of the environment through toxic pollutants poses a key risk to the environment due to irreversible environmental damage(s). Industrialization and urbanization produced harmful elements such as petrochemicals, agrochemicals, pharmaceuticals, nanomaterials, and herbicides that are intentionally or unintentionally released into the water system, threatening biodiversity, the health of animals, and humans. Heavy metals (HMs) in water, for example, can exist in a variety of forms that are inclined by climate features like the presence of various types of organic matter, pH, water system hardness, transformation, and bioavailability. Biological treatment is an important tool for removing toxic contaminants from the ecosystem, and it has piqued the concern of investigators over the centuries. In situ bioremediation such as biosparging, bioventing, biostimulation, bioaugmentation, and phytoremediation and ex-situ bioremediation includes composting, land farming, biopiles, and bioreactors. In the last few years, scientific understanding of microbial relations with particular chemicals has aided in the protection of the environment. Despite intensive studies being carried out on the mitigation of toxic pollutants, there have been limited efforts performed to discuss the solutions to tackle the limitations and approaches for the remediation of heavy metals holistically. This paper summarizes the risk assessment of HMs on aquatic creatures, the environment, humans, and animals. The content of this paper highlights the principles and limitations of microbial remediation to address the technological challenges. The coming prospect and tasks of evaluating the impact of different treatment skills for pollutant remediation have been reviewed in detail. Moreover, genetically engineered microbes have emerged as powerful bioremediation capabilities with significant potential for expelling toxic elements. With appropriate examples, current challenging issues and boundaries related to the deployment of genetically engineered microbes as bioremediation on polluted soils are emphasized.

Sustainable strategies for combating hydrocarbon pollution: Special emphasis on mobil oil bioremediation.

The global rise in industrialization and vehicularization has led to the increasing trend in the use of different crude oil types. Among these mobil oil has major application in automobiles and different machines. The combustion of mobil oil renders a non-usable form that ultimately enters the environment thereby causing problems to environmental health. The aliphatic and aromatic hydrocarbon fraction of mobil oil has serious human and environmental health hazards. These components upon interaction with soil affect its fertility and microbial diversity. The recent advancement in the omics approach viz. metagenomics, metatranscriptomics and metaproteomics has led to increased efficiency for the use of microbial based remediation strategy. Additionally, the use of biosurfactants further aids in increasing the bioavailability and thus biodegradation of crude oil constituents. The combination of more than one approach could serve as an effective tool for efficient reduction of oil contamination from diverse ecosystems. To the best of our knowledge only a few publications on mobil oil have been published in the last decade. This systematic review could be extremely useful in designing a micro-bioremediation strategy for aquatic and terrestrial ecosystems contaminated with mobil oil or petroleum hydrocarbons that is both efficient and feasible. The state-of-art information and future research directions have been discussed to address the issue efficiently.

Effect of algae (Scenedesmus obliquus) biomass pre-treatment on bio-oil production in hydrothermal liquefaction (HTL): Biochar and aqueous phase utilization studies.

Environmental concerns due to fossil fuel usage has turned the research interest towards biomass and bioenergy field. Renewable biomass such as microalgae provides numerous advantages as they can grow in wastewater; sequester carbon dioxide, economical and eco-friendly. In this study, effect of pretreatment of microalgae (Scenedesmus obliquus) biomass using post-hydrothermal liquefaction wastewater (PHWW) for bio-oil production through hydrothermal liquefaction at a temperature of 300 °C was studied. Results showed liquefaction of pre-treated biomass yielded 48.53% bio-oil whereas 28.35% was resulted from biomass without pretreatment. The analysis of higher heating value of bio-oil showed that pretreated biomass oil has 36.19 MJ.Kg-1 against non-pretreated biomass oil, which has 28.88 MJ.Kg-1. Bio-oil (pretreated biomass) analysis revealed that 60% of compounds are in diesel and gasoline range with 58.09% of energy recovery. Bio-oil was rich in hydrocarbons of C7-C21 range with less oxygenated compounds. Carbon balance showed that an increase of 13% of carbon was sequestered in solid residue obtained from pretreated biomass and about 146% of increase also obtained in bio-oil.

Enhancing anaerobic digestion for rural wastewater treatment with granular activated carbon (GAC) supplementation.

Notwithstanding many efforts to increase the efficiency of anaerobic digestion at low-temperature (winter) conditions, a cost-effective and efficient method is lacking. This study proposes a low-cost method of low-temperature (<35 °C) anaerobic digestion of wastewater, involving supplementation with granular activated carbon (GAC). Supplementation with GAC was found to reduce the lag time by 29.8% (from 15.1 to 10.6 days) and increase the maximum methane production rate by 23.4% (from 6.4 to 7.9 mL/day) at 25 °C. Network analysis demonstrated a strong co-occurrence of Syntrophobacteriales and hydrogenotrophic methanogens (Methanobacteriaceae; WSA2; Methanoregulaceae). GAC supplementation can drastically reduce the time required for organic matter decomposition and methane production, thereby increase the efficiency of wastewater treatment.

Conversion of waste cooking oil into biodiesel using heterogenous catalyst derived from cork biochar.

In this study, a heterogeneous catalyst prepared by pyrolysis of waste cork (Quercus suber) was used for the transesterification of waste cooking oil (WCO). Physicochemical properties of the synthesized biochar catalyst were studied using BET, SEM, FTIR, and XRD. The experiment results demonstrate that heterogeneous catalyst synthesized at 600 °C showed maximum fatty acids methyl esters (FAMEs) conversion (98%) at alcohol:oil (25:1), catalyst loading (1.5% w/v) and temperature 65 °C. Biodiesel produced from WCO (Canola oil) mainly composed of FAMEs in following order C18:1 > C18:2 > C16:0 > C18:0 > C20:0. Properties of produced biodiesel were analysed as cetane number (CN) 50.56, higher heating value (HHV) 39.5, kinematic viscosity (ʋ) 3.9, and density (ρ) 0.87.

Photoautotrophic cultivation of mixed microalgae consortia using various organic waste streams towards remediation and resource recovery.

In this study, mixed microalgae consortia was cultivated using digestate (D), animal manure (AM) and textile wastewater (TW) as growth medium providing mainly N (nitrogen) and P (phosphorous) sources without any extra nutrient addition. The corresponding total nitrogen (TN) and total phosphorous (TP, PO3-P) concentrations were noted as 323 and 21 for AM, 481 and 31 for TW and 747 and 55mg/L for D, respectively. After a cultivation period of 13days, P were completely removed (100%), however, N was still remain and attained the removal rate of 70.1, 72.3 and 16.7% for TW, AM and D, respectively. The peak growth rate and biomass production of 0.419d-1 and 0.4g/L (in terms of volatile solids, VS) was achieved using TW as growth medium.

Production of (3-hydroxybutyrate-co-3-hydroxyhexanoate) copolymer from coffee waste oil using engineered Ralstonia eutropha.

Polyhydroxyalkonate (PHA) is a type of polymer that has the potential to replace petro-based plastics. To make PHA production more economically feasible, there is a need to find a new carbon source and engineer microbes to produce a commercially valuable polymer. Coffee waste is an inexpensive raw material that contains fatty acids. It can act as a sustainable carbon source and seems quite promising with PHA production in Ralstonia eutropha, which is a well-known microbe for PHA accumulation, and has the potential to utilize fatty acids. In this study, to make poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (P(HB-co-HHx)), which has superior properties in terms of biodegradability, biocompatibility, and mechanical strength, engineered strain Ralstonia eutropha Re2133 overexpressing (R)-specific enoyl coenzyme-A hydratase (phaJ) and PHA synthetase (phaC2) with deletion of acetoacetyl Co-A reductases (phaB1, phaB2, and phaB3) was used to produce PHA from coffee waste oil. At a coffee oil concentration of 1.5%, and C/N ratio of 20, the R. eutropha Re2133 fermentation process results in 69% w/w of DCW PHA accumulation and consists of HB (78 mol%) and HHx (22 mol%). This shows the feasibility of using coffee waste oil for P(HB-co-HHx) production, as it is a low-cost fatty acid enriched waste material.

Mesophilic co-digestion of palm oil mill effluent and empty fruit bunches.

The palm oil mill industry generates palm oil mill effluent (POME) and empty fruit bunches (EFB) as by-products. This study reports the mesophilic co-digestion of POME with EFB. The biochemical methane potential (BMP) of POME and EFB was 0.397 L CH4/g volatile solids (VS) and 0.264 L CH4/g VS, respectively. In a series of batch tests at various EFB to POME ratios, the maximum methane production rate was achieved at an EFB:POME ratio of 0.25-0.31:1. Performance data from lab-scale digesters confirmed the positive synergism by the addition of EFB to POME, which was attributed to the balanced chemical composition, for example the chemical oxygen demand (COD) to total Kjeldahl nitrogen (TKN) ratio. The EFB addition enhanced the acceptable organic loading rate, methane production, COD removal, and microbial activity. The mesophilic co-digestion of POME and EFB promises to be a viable recycling method to alleviate pollution problems and recover renewable energy in the palm oil mill industry.