Providencia sp. strain X1 showing the highest xylanase activity among six bacterial isolates was isolated from saw-dust decomposing site. Strain X1 produced cellulase-free extracellular xylanase, ...which was higher in wheat bran medium than in xylan medium, when cultivated at pH 8.0 and 35°C. Zymogram analysis of crude preparation of enzymes obtained while growing on wheat bran and birchwood xylan revealed the presence of seven and two distinct xylanases with estimated molecular weight of 33; 35; 40; 48; 60; 75; and 95 kDa and 33 and 44 kDa, respectively. The crude xylanases were produced on wheat bran medium and showed optimum activity at pH 9.0 and 60°C. The thermotolerance studies showed activity retention of 100% and 85% at 40°C and 60°C after 30 min preincubation at pH 9.0. It was tolerant to lignin, ferulic acid, syringic acid, and guaiacol and retained 90% activity after ethanol treatment. The enzyme preparation was also tolerant to methanol and acetone and showed good activity retention in the presence of metal ions such as Fe2+, Mg2+, Zn2+, and Ca2+. The crude enzyme preparation was classified as endoxylanase based on the product pattern of xylan hydrolysis. Pretreatment of kraft pulp with crude xylanases for 3 h at 60°C led to a decrease in kappa number by 28.5%. The properties of present xylanases make them potentially useful for industrial applications.
The microbial community in biofilm is safeguarded from the action of toxic chemicals, antimicrobial compounds, and harsh/stressful environmental circumstances. Therefore, biofilm-based technology has ...nowadays become a successful alternative for treating industrial wastewater as compared to suspended growth-based technologies. In biofilm reactors, microbial cells are attached to static or free-moving materials to form a biofilm which facilitates the process of liquid and solid separation in biofilm-mediated operations. This paper aims to review the state-of-the-art of recent research on bacterial biofilm in industrial wastewater treatment including biofilm fundamentals, possible applications and problems, and factors to regulate biofilm formation. We discussed in detail the treatment efficiencies of fluidized bed biofilm reactor (FBBR), trickling filter reactor (TFR), rotating biological contactor (RBC), membrane biofilm reactor (MBfR), and moving bed biofilm reactor (MBBR) for different types of industrial wastewater treatment. Besides, biofilms have many applications in food and agriculture, biofuel and bioenergy production, power generation, and plastic degradation. Furthermore, key factors for regulating biofilm formation were also emphasized. In conclusion, industrial applications make evident that biofilm-based treatment technology is impactful for pollutant removal. Future research to address and improve the limitations of biofilm-based technology in wastewater treatment is also discussed.
Biofilm formation ability of bacteria makes them potential in the field of tannery effluent treatment. However, the hazardous nature of effluent and environmental conditions may disturb the biofilm ...formation ability of bacteria which ultimately affects their effluent treatment efficiency. Accordingly, we isolated and characterized biofilm-forming bacteria Bacillus vallismortis (MT027009), Bacillus haynesii (MT027008), and Alcaligenes aquatilis (MT027005) from tannery sludge and examined them for biofilm formation under variable environmental conditions. Biofilm formation in tryptic soy broth (TSB) at different incubation times (24–120 h) revealed that the biofilm formation activity of the strain B. haynesii was not affected by incubation time, whereas the increase in biofilm formation was observed in the case of B. vallismortis (28 %) and A. aquatilis (52 %) after 48 h. The medium pH (pH 5.0–9.0) had a limited effect on biofilm formation except in the case of A. aquatilis at pH 5.0 (94 %) and pH 9.0 (80 %). Furthermore, compared to the controls (only TSB), the strains B. vallismortis, B. haynesii, and A. aquatilis showed enhanced biofilm formation in undiluted tannery effluent (28, 33, and 21 %) and 25 mg L−1 Cr(VI) (23 %, 48 % 32 %). The biofilm structure was influenced by Cr(VI) as revealed by scanning electron microscopy (SEM) analysis. The results of Cr(VI) bioreduction studies suggest that bacterial biofilm (60–99 %) has a greater potential to remove Cr(VI) than planktonic cells (43–94 %). The results of the study provide important data on biofilm formation by indigenous bacteria in effluent environment conditions, making them potential isolates for tannery effluent treatment.
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•Formation of biofilm under mixed culture conditions.•Tannery effluent and Cr(VI) induced biofilm formation from 20 to 62 %.•Biofilm formation and Cr(VI) reduction were maximum by B. haynesii.•Cr(VI) reduction was 60–99 % from bacterial biofilm.
The feasibility of in-silico techniques, together with the computational framework, has been applied to predictive bioremediation aiming to clean-up contaminants, toxicity evaluation, and ...possibilities for the degradation of complex recalcitrant compounds. Emerging contaminants from different industries have posed a significant hazard to the environment and public health. Given current bioremediation strategies, it is often a failure or inadequate for sustainable mitigation of hazardous pollutants. However, clear-cut vital information about biodegradation is quite incomplete from a conventional remediation techniques perspective. Lacking complete information on bio-transformed compounds leads to seeking alternative methods. Only scarce information about the transformed products and toxicity profile is available in the published literature. To fulfill this literature gap, various computational or in-silico technologies have emerged as alternating techniques, which are being recognized as in-silico approaches for bioremediation. Molecular docking, molecular dynamics simulation, and biodegradation pathways predictions are the vital part of predictive biodegradation, including the Quantitative Structure-Activity Relationship (QSAR), Quantitative structure-biodegradation relationship (QSBR) model system. Furthermore, machine learning (ML), artificial neural network (ANN), genetic algorithm (GA) based programs offer simultaneous biodegradation prediction along with toxicity and environmental fate prediction. Herein, we spotlight the feasibility of in-silico remediation approaches for various persistent, recalcitrant contaminants while traditional bioremediation fails to mitigate such pollutants. Such could be addressed by exploiting described model systems and algorithm-based programs. Furthermore, recent advances in QSAR modeling, algorithm, and dedicated biodegradation prediction system have been summarized with unique attributes.
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•Herein, trends in predictive biodegradation to mitigate environmental pollutants are reviewed.•In-silico technologies have emerged as alternating techniques for bioremediation.•Molecular docking, and molecular dynamics simulation are the vital part of predictive biodegradation.•Rule-based pathways prediction systems for predictive biodegradation have been explained with recent updates.•In-silico toxicity prediction as a part of hazard assessment also explained at a glance.
Enzyme immobilization is an exciting alternative to improve the stability of enzymatic processes and economic viability in terms of reusability. In the current study, purified xylanase from B. ...licheniformis Alk-1 was immobilized within glutaraldehyde activated calcium alginate beads and characterized in respect of free enzyme. Immobilization increases the optimum pH and temperature of entrapped and cross-linked enzyme from pH=8.0 to 9.0 and 50–60°C. The kinetics parameter of immobilized (cross-linked) enzyme showed an increase in Km (from 4.36mg/mL to 5.38mg/mL) and decrease in Vmax (from 383 IU/mg/min to 370 IU/mg/min). Immobilization increases the optimum reaction time for xylan degradation of immobilized xylanase from 15 to 30min when compare to free form. The storage stability study suggested that the immobilized enzyme retains 80% of its original activity at 4°C after 30days compared to free enzyme (5%). Further, immobilization improved enzyme stability in presence of different additives. The immobilized (cross-linked) enzyme also exhibited adequate recycling efficiency up to five reaction cycles with 37% retention activity. The finding of this study suggests improvement of overall performance of immobilized xylanase in respect to free form and can be used to make a bioreactor for various applications such as poultry feed preparations.
Lignin modifying enzymes from fungi and bacteria are potential biocatalysts for sustainable mitigation of different potentially toxic pollutants in wastewater. Notably, the paper and pulp industry ...generates enormous amounts of wastewater containing high amounts of complex lignin-derived chlorinated phenolics and sulfonated pollutants. The presence of these compounds in wastewater is a critical issue from environmental and toxicological perspectives. Some chloro-phenols are harmful to the environment and human health, as they exert carcinogenic, mutagenic, cytotoxic, and endocrine-disrupting effects. In order to address these most urgent concerns, the use of oxidative lignin modifying enzymes for bioremediation has come into focus. These enzymes catalyze modification of phenolic and non-phenolic lignin-derived substances, and include laccase and a range of peroxidases, specifically lignin peroxidase (LiP), manganese peroxidase (MnP), versatile peroxidase (VP), and dye-decolorizing peroxidase (DyP). In this review, we explore the key pollutant-generating steps in paper and pulp processing, summarize the most recently reported toxicological effects of industrial lignin-derived phenolic compounds, especially chlorinated phenolic pollutants, and outline bioremediation approaches for pollutant mitigation in wastewater from this industry, emphasizing the oxidative catalytic potential of oxidative lignin modifying enzymes in this regard. We highlight other emerging biotechnical approaches, including phytobioremediation, bioaugmentation, Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-based technology, protein engineering, and degradation pathways prediction, that are currently gathering momentum for the mitigation of wastewater pollutants. Finally, we address current research needs and options for maximizing sustainable biobased and biocatalytic degradation of toxic industrial wastewater pollutants.
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•Systematic outline of key pollutant-generating steps in the paper and pulp industry•Toxic pollutants chemistry and their environmental and human health impact•Novel bioremediation approaches for pollutant mitigation in wastewater•Oxidative catalytic potential of lignin modifying enzymes in wastewater treatment•Summary of forward-looking biotechnology tools to advance biobased remediation
Microalgae are recognized as cell factories enriched with biochemicals suitable as feedstock for bio-energy, food, feed, pharmaceuticals, and nutraceuticals applications. The industrial application ...of microalgae is challenging due to hurdles associated with mass cultivation and biomass recovery. The scale-up production of microalgal biomass in freshwater is not a sustainable solution due to the projected increase of freshwater demands in the coming years. Microalgae cultivation in wastewater is encouraged in recent years for sustainable bioeconomy from biorefinery processes. Wastewater from the food industry is a less-toxic growth medium for microalgal biomass production. Traditional wastewater treatment and management processes are expensive; hence it is highly relevant to use low-cost wastewater treatment processes with revenue generation through different products. Microalgae are accepted as potential biocatalysts for the bioremediation of wastewater. Microalgae based purification of wastewater technology could be a universal alternative solution for the recovery of resources from wastewater for low-cost biomass feedstock for industry. This review highlights the importance of microalgal biomass production in food processing wastewater, their characteristics, and different microalgal cultivation methods, followed by nutrient absorption mechanisms. Towards the end of the review, different microalgae biomass harvesting processes with biorefinery products, and void gaps that tend to hinder the biomass production with future perspectives will be intended. Thus, the review could claim to be valuable for sustainable microalgae biomass production for eco-friendly bioproduct conversions.
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In this study, the efficiency of free and immobilized cells of newly isolated hexavalent chromium Cr(VI) reducing Bacillus cereus strain Cr1 (accession no. KJ162160) was studied in the treatment of ...tannery effluent. The analysis of effluents revealed high chemical oxygen demand (COD-1260 mg/L), biological oxygen demand (BOD5-660 mg/L), total dissolved solids (TDS-14000 mg/L), electrical conductivity (EC-21.5 mS/cm) and total chromium (TC-2.4 mg/L). The effluents also showed genotoxic effects to Allium cepa. Treatment of tannery effluent with isolated B. cereus strain led to considerable reduction of pollutant load. The pollutant load reduction was studied with both immobilized and free cells and immobilized cells were more effective in reducing COD (65%), BOD (80%), TDS (67%), EC (65%) and TC (92%) after 48 h. GC-MS analysis of pre and post-treatment tannery effluent samples revealed reduction of organic load after treatment with free and immobilized cells. An improvement in mitotic index and reduction in chromosomal aberrations was also observed in A. cepa grown with post-treatement effluent samples compared to untreated sample. Results demonstrate that both methods of bacterial treatment (free and immobilized) were efficient in reducing the pollutant load of tannery effluent as well as in reducing genotoxic effects, however, treatment with immobilized cells was more effective.
•Novel chromium (VI)-reducing Bacillus cereus strain Cr1was isolated.•Bacterial treatment of effluent led to noticeable reduction in pollutant load.•Allium cepa bioassay showed reduced genotoxicity of treated effluent.
•Biofilm-forming bacterium E. faecium is isolated and characterized.•Temperature 28 °C and pH 7.5 were optimum for biofilm formation.•Tannery effluent and metal Ion (Cd, Cr(VI) and Ni) induced ...biofilm formation.•The E. faecium treated tannery effluent was less toxic.
Treatment of tannery effluent (TE) using bacterial biofilm is a trending approach in the current scenario, due to greater survival and adaptation in stress conditions. The present study is concerned with the characterization of biofilm-forming bacterium Enterococcus faecium from tannery sludge and the investigation of their activity under different physiological conditions. Biofilm formation by E. faecium was strongly affected by variable physiological conditions. The optimum conditions were pH 7.5, temperature 28 °C, incubation time up to 96 h, glucose 1%, yeast extract 0.1–0.5%, NaCl 0.1–0.5%, tannery effluent-TE up to 50% v/v and Cd, Cr (VI) and Ni from 0.25 to 0.5 mM. Further, E. faecium treated TE was less phytotoxic on the fenugreek plant than the TE treated by non-biofilm forming isolate. The toxicity of TE could be reduced by the potentially biofilm-forming bacteria, which may be used in the bioremediation process.
This investigation uses in situ high-resolution transmission electron microscopy to quantify the atomic-level dynamic behavior of a diffuse interphase boundary between ordered and disordered phases ...in an Au–Cu alloy at elevated temperature. It is found that both the interphase boundary position and thickness fluctuate with time and that the behavior of the disordered side of the interphase boundary differs from that of the ordered side. Analysis of the interphase boundary shape shows that it fluctuates by a mechanism involving the collective motion of many atoms rather than by single-atom jumps. These features are explained in terms of the physical properties of the different phases at the interphase boundary.
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