Genomic analysis of carbon dioxide sequestering bacterium for exopolysaccharides production

Chemical and biological effects of zero-valent iron (ZVI) concentration on in-situ production of H2 from ZVI and bioconversion of CO2 into CH4 under anaerobic conditions

The conversion of carbon dioxide (CO2) to methane (CH4) is a strategy for sequestering CO2. Zero-valent iron (ZVI) has been proposed as an alternative electron donor for the CO2 reduction to CH4. In this study, the effects of ZVI concentrations on the abiotic production of H2 (without the action of microorganisms) in the first part and on the biological conversion of CO2 to CH4 using ZVI as a direct electron donor in the second part were examined. In the abiotic H2 production, the increase in the ZVI concentration from 16 to 32, 64, and 96 g/L was found to have positive effects on both the amounts of H2 generated and the rates of H2 production because the extent of ZVI oxidation positively correlates with increasing surface area. Nevertheless, the increase in ZVI concentration from 96 to 224 g/L did not benefit the H2 production because the ZVI dissolution was suppressed by the increasing aqueous pH above 10. In the bioconversion of CO2 to CH4 using ZVI as an electron donor, the main methanogenesis pathway occurred via hydrogenotrophic methanogenesis at pH 8.7-9.5 driven by the genus Methanobacterium of the class Methanobacteria. At ZVI concentrations of 64 g/L and above, the production of volatile fatty acid (VFA) became clear. Acetate was the main VFA, indicating the induction of homoacetogenesis at ZVI concentrations of 64 g/L and above. In addition, the presence of propionate as the second major VFA suggests the production of propionate from CO2 and acetate under conditions with high H2 partial pressure. The results indicated that the pathway for ZVI/CO2 conversion to CH4 was competitive between hydrogenotrophic methanogenesis and homoacetogenesis.

Eco-friendly approaches for mitigating plastic pollution: advancements and implications for a greener future

Plastic pollution has become a global problem since the extensive use of plastic in industries such as packaging, electronics, manufacturing and construction, healthcare, transportation, and others. This has resulted in an environmental burden that is continually growing, which has inspired many scientists as well as environmentalists to come up with creative solutions to deal with this problem. Numerous studies have been reviewed to determine practical, affordable, and environmentally friendly solutions to regulate plastic waste by leveraging microbes' innate abilities to naturally decompose polymers. Enzymatic breakdown of plastics has been proposed to serve this goal since the discovery of enzymes from microbial sources that truly interact with plastic in its naturalistic environment and because it is a much faster and more effective method than others. The scope of diverse microbes and associated enzymes in polymer breakdown is highlighted in the current review. The use of co-cultures or microbial consortium-based techniques for the improved breakdown of plastic products and the generation of high-value end products that may be utilized as prototypes of bioenergy sources is highlighted. The review also offers a thorough overview of the developments in the microbiological and enzymatic biological degradation of plastics, as well as several elements that impact this process for the survival of our planet.

Arsenic pollution remediation mechanism and preliminary application of arsenic-oxidizing bacteria isolated from industrial wastewater

Microbial remediation is vital for improving heavy metal-polluted water. In this work, two bacterial strains, K1 (Acinetobacter gandensis) and K7 (Delftiatsuruhatensis), with high tolerance to and strong oxidation of arsenite [As(III)], were screened from industrial wastewater samples. These strains tolerated 6800 mg/L As(III) in a solid medium and 3000 mg/L (K1) and 2000 mg/L (K7) As(III) in a liquid medium; arsenic (As) pollution was repaired through oxidation and adsorption. The As(III) oxidation rates of K1 and K7 were the highest at 24 h (85.00 ± 0.86%) and 12 h (92.40 ± 0.78%), respectively, and the maximum gene expression levels of As oxidase in these strains were observed at 24 and 12 h. The As(III) adsorption efficiencies of K1 and K7 were 30.70 ± 0.93% and 43.40 ± 1.10% at 24 h, respectively. The strains exchanged and formed a complex with As(III) through the -OH, -CH3, and C]O groups, amide bonds, and carboxyl groups on the cell surfaces. When the two strains were co-immobilized with Chlorella, the adsorption efficiency of As(III) improved (76.46 ± 0.96%) within 180 min, thereby exhibiting good adsorption and removal effects of other heavy metals and pollutants. These results outlined an efficient and environmentally friendly method for the cleaner production of industrial wastewater.

Recent Advances in Micro-/Nanoplastic (MNPs) Removal by Microalgae and Possible Integrated Routes of Energy Recovery

Reliance on plastic has resulted in the widespread occurrence of micro-/nanoplastics (MNPs) in aquatic ecosystems, threatening the food web and whole ecosystem functions. There is a tight interaction between MNPs and microalgae, as dominant living organisms and fundamental constituents at the base of the aquatic food web. Therefore, it is crucial to better understand the mechanisms underlying the interactions between plastic particles and microalgae, as well as the role of microalgae in removing MNPs from aquatic ecosystems. In addition, finding a suitable route for further utilization of MNP-contaminated algal biomass is of great importance. The present review article provides an interdisciplinary approach to elucidate microalgae-MNP interactions and subsequent impacts on microalgal physiology. The degradation of plastic in the environment and differences between micro- and nanoplastics are discussed. The possible toxic effects of MNPs on microalgal growth, photosynthetic activity, and morphology, due to physical or chemical interactions, are evaluated. In addition, the potential role of MNPs in microalgae cultivation and/or harvesting, together with further safe routes for biomass utilization in biofuel production, are suggested. Overall, the current article represents a state-of-the-art overview of MNP generation and the consequences of their accumulation in the environment, providing new insights into microalgae integrated routes of plastic removal and bioenergy production.

Enzymatic Dispersion of Biofilms: An Emerging Biocatalytic Avenue to Combat Biofilm-Mediated Microbial Infections

Drug resistance by pathogenic microbes has emerged as a matter of great concern to mankind. Microorganisms such as bacteria and fungi employ multiple defense mechanisms against drugs and the host immune system. A major line of microbial defense is the biofilm, which comprises extracellular polymeric substances that are produced by the population of microorganisms. Around 80% of chronic bacterial infections are associated with biofilms. The presence of biofilms can increase the necessity of doses of certain antibiotics up to 1000-fold to combat infection. Thus, there is an urgent need for strategies to eradicate biofilms. Although a few physicochemical methods have been developed to prevent and treat biofilms, these methods have poor efficacy and biocompatibility. In this review, we discuss the existing strategies to combat biofilms and their challenges. Subsequently, we spotlight the potential of enzymes, in particular, polysaccharide degrading enzymes, for biofilm dispersion, which might lead to facile antimicrobial treatment of biofilm-associated infections.

Extracellular Polymeric Substances Drive Symbiotic Interactions in Bacterial‒Microalgal Consortia

The importance of several factors that drive the symbiotic interactions between bacteria and microalgae in consortia has been well realised. However, the implication of extracellular polymeric substances (EPS) released by the partners remains unclear. Therefore, the present study focused on the influence of EPS in developing consortia of a bacterium, Variovorax paradoxus IS1, with a microalga, Tetradesmus obliquus IS2 or Coelastrella sp. IS3, all isolated from poultry slaughterhouse wastewater. The bacterium increased the specific growth rates of microalgal species significantly in the consortia by enhancing the uptake of nitrate (88‒99%) and phosphate (92‒95%) besides accumulating higher amounts of carbohydrates and proteins. The EPS obtained from exudates, collected from the bacterial or microalgal cultures, contained numerous phytohormones, vitamins, polysaccharides and amino acids that are likely involved in interspecies interactions. The addition of EPS obtained from V. paradoxus IS1 to the culture medium doubled the growth of both the microalgal strains. The EPS collected from T. obliquus IS2 significantly increased the growth of V. paradoxus IS1, but there was no apparent change in bacterial growth when it was cultured in the presence of EPS from Coelastrella sp. IS3. These observations indicate that the interaction between V. paradoxus IS1 and T. obliquus IS2 was mutualism, while commensalism was the interaction between the bacterial strain and Coelastrella sp. IS3. Our present findings thus, for the first time, unveil the EPS-induced symbiotic interactions among the partners involved in bacterial‒microalgal consortia.

Lipolytic Nocardiopsis for reduction of pollution load in textile industry effluent and SWISS model for structural study of lipase

The aim of this work was to study the reduction of pollution load in the textile industry effluent by lipase producing Nocardiopsis alba. Nocardiopsis alba was isolated from the soap-stock of an oil refinery located in North Gujarat, India. Lipase 2 (EC 3.1.1.3) protein sequence was identified from Nocardiopsis alba and the 3D model was predicted by SWISS Modeling. Lipolytic Nocardiopsis alba showed 84 ± 0.3 %, 75 ± 0.4 %, and 81 ± 0.3 % reduction of Chemical Oxygen Demand, Biochemical Oxygen Demand and Total Solids, respectively when was grown in textile industrial wastewater at 37 ± 1 °C, 120 rpm for 15 days. The findings of this research offer potential environmental benefits along with socio-economic benefits as well if implemented suitably.

CO2 biocapture by Scenedesmus sp. grown in industrial wastewater

Greenhouse gases (GHG) emissions are widely related to climate change, triggering several environmental problems of global concern and producing environmental, social, and economic negative impacts. Therefore, global research seeks to mitigate greenhouse gas emissions. On the other hand, the use of wastes under a circular economy scheme generates subproducts from the range of high to medium-value, representing a way to help sustainable development. Therefore, the use of wastewater as a culture medium to grow microalgae strains that biocapture environmental CO₂, is a proposal with high potential to reduce the GHG presence in the environment. In this work, Scenedesmus sp. was cultivated using BG-11 medium and industrial wastewater (IWW) as a culture medium with three different CO₂ concentrations, 0.03%, 10%, and 20% to determine their CO₂ biocapture potential. Furthermore, the concomitant removal of COD, nitrates, and total phosphorus in wastewater was evaluated. Scenedesmus sp. achieves a biomass concentration of 1.9 g L^-1 when is grown in BG-11 medium, 0.69 g L^-1 when is grown in a combination of BG-11 medium and 25% of industrial wastewater; both cases with 20% CO₂ supplied. The maximum CO₂ removal efficiency (8.4%, 446 ± 150 mg CO₂ L^-1 day^-1) was obtained with 10% CO₂ supplied and using a combination of BG-11 medium and 50% IWW (T2). Also, the highest removal of COD was reached with a combination of BG-11 medium and T2 with a supply of 20% CO₂ (82% of COD removal). Besides, the highest nitrates removal was achieved with a combination of BG-11 medium and 75% IWW (T3) with a supply of 10% CO₂ (42% of nitrates removal) and the maximum TP removal was performed with the combination of BG-11 medium and 25% IWW (T1) with a supply of 10% CO₂ (67% of TP removal). These results indicate that industrial wastewater can be used as a culture media for microalgae growth and CO₂ biocapture can be performed as concomitant processes.

Structural Characterisation and Assessment of the Novel Bacillus amyloliquefaciens RK3 Exopolysaccharide on the Improvement of Cognitive Function in Alzheimer's Disease Mice

In this study Bacillus amyloliquefaciens RK3 was isolated from a sugar mill effluent-contaminated soil and utilised to generate a potential polysaccharide with anti-Alzheimer's activity. Traditional and molecular methods were used to validate the strain. The polysaccharide produced by B. amyloliquefaciens RK3 was purified, and the yield was estimated to be 10.35 gL^-1. Following purification, the polysaccharide was structurally and chemically analysed. The structural analysis revealed the polysaccharide consists of α-d-mannopyranose (α-d-Manp) and β-d-galactopyranose (β-d-Galp) monosaccharide units connected through glycosidic linkages (i.e., β-d-Galp(1→6)β-d-Galp (1→6)β-d-Galp(1→2)β-d-Galp(1→2)[β-d-Galp(1→6)]β-d-Galp(1→2)α-d-Manp(1→6)α-d-Manp (1→6)α-d-Manp(1→6)α-d-Manp(1→6)α-d-Manp). The scanning electron microscopy and energy-dispersive X-ray spectroscopy imaging of polysaccharides emphasise their compactness and branching in the usual tubular heteropolysaccharide structure. The purified exopolysaccharide significantly impacted the plaques formed by the amyloid proteins during Alzheimer's disease. Further, the results also highlighted the potential applicability of exopolysaccharide in various industrial and pharmaceutical applications.

Traditional System Versus DNA Barcoding in Identification of Bamboo Species: A Systematic Review

Bamboo, a gramineous plant belonging to the family Poaceae, comprises of 1575 species from 116 genera across the globe. It has the ability to grow and evolve on degraded land and hence, can be utilized in the various applications as an alternative for plastic and wood. DNA barcoding, a long genomic sequence, identifies barcode region which shows species-specific nucleotide differences. This technology is considered as advanced molecular technique utilized for characterization and classification of the various species by applying distinctive molecular markers. Recent investigations revealed the potential application of various barcode regions such as matK, rbcL, rpoB, rpoC1, psbA-trnH, and ITS2, in identification of many bamboo species from different genus. In this review we comprehensively discussed the relevance of DNA barcoding as a tool in classification/identification of various bamboo species. We highlighted the methodology, how this advance technology overcomes the challenges associated with traditional methods along with prospects for future research.

Prospective bioremediation of toxic heavy metals in water by surfactant exopolysaccharide of Ochrobactrum pseudintermedium using cost-effective substrate

Globally, the underlying peril of cumulative toxicity of heavy metals in water bodies contaminated by industrial effluents is a matter of great concern to the environmentalists. Heavy metals like lead, cadmium, and nickel are particularly liable for this. Such toxic water is not only hazardous to human health but also harmful to aquatic animals. Remedial measures are being taken by physico-chemical techniques, but most of them are neither eco-friendly nor cost-effective. Biological means like bioaccumulation of heavy metals by viable bacteria are often tedious. In the present study, biosorption of heavy metals is successfully expedited by surfactant exopolysaccharide (SEPS) of Ochrobactrum pseudintermedium C1 as a simple, safe, and economically sustainable option utilizing an easily available and cost-effective substrate like molasses extract. Its efficacy in bioremediation of toxic heavy metals like cadmium, nickel, and lead have been studied by UV-Vis spectrophotometry and verified by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). FTIR and zeta potential studies have also been carried out to explore this novel biosorption potential. Results are conclusive and promising. Moreover, this particular SEPS alone can remediate all these three toxic heavy metals in water. For futuristic applications, it might be a prospective and cost-effective resource for bioremediation of toxic heavy metals in aqueous environment.

Effects of an EPS Biosynthesis Gene Cluster of Paenibacillus polymyxa WLY78 on Biofilm Formation and Nitrogen Fixation under Aerobic Conditions

Exopolysaccharides (EPS) are of high significance in bacterial biofilm formation. However, the effects of EPS cluster(s) on biofilm formation in Paenibacillus species are little known. In this study, we have shown that Paenibacillus polymyxa WLY78, a N₂-fixing bacterium, can form biofilm. EPS is the major component of the extracellular matrix. The genome of P. polymyxa WLY78 contains two putative gene clusters (designated pep-1 cluster and pep-2 cluster). The pep-1 cluster is composed of 12 putative genes (pepO-lytR) co-located in a 13 kb region. The pep-2 cluster contains 17 putative genes (pepA-pepN) organized as an operon in a 20 kb region. Mutation analysis reveals that the pep-2 cluster is involved in EPS biosynthesis and biofilm formation. Disruption of the pep-2 cluster also leads to the enhancement of motility and change of the colony morphology. In contrast, disruption of the pep-1 cluster does not affect EPS synthesis or biofilm formation. More importantly, the biofilm allowed P. polymyxa WLY78 to fix nitrogen in aerobic conditions, suggesting that biofilm may provide a microaerobic environment for nitrogenase synthesis and activity.

Genomic analysis of Bacillus cereus NWUAB01 and its heavy metal removal from polluted soil

Microorganisms that display unique biotechnological characteristics are usually selected for industrial applications. Bacillus cereus NWUAB01 was isolated from a mining soil and its heavy metal resistance was determined on Luria-Bertani agar. The biosurfactant production was determined by screening methods such as drop collapse, emulsification and surface tension measurement. The biosurfactant produced was evaluated for metal removal (100 mg/L of each metal) from contaminated soil. The genome of the organism was sequenced using Illumina Miseq platform. Strain NWUAB01 tolerated 200 mg/L of Cd and Cr, and was also tolerant to 1000 mg/L of Pb. The biosurfactant was characterised as a lipopeptide with a metal-complexing property. The biosurfactant had a surface tension of 39.5 mN/m with metal removal efficiency of 69%, 54% and 43% for Pb, Cd and Cr respectively. The genome revealed genes responsible for metal transport/resistance and biosynthetic gene clusters involved in the synthesis of various secondary metabolites. Putative genes for transport/resistance to cadmium, chromium, copper, arsenic, lead and zinc were present in the genome. Genes responsible for biopolymer synthesis were also present in the genome. This study highlights biosurfactant production and heavy metal removal of strain NWUAB01 that can be harnessed for biotechnological applications.