Marine bacteria and omic approaches: A novel and potential repository for bioremediation assessment.

Marine environments accommodating diverse assortments of life constitute a great pool of differentiated natural resources. The cumulative need to remedy unpropitious effects of anthropogenic activities on estuaries and coastal marine ecosystems has propelled the development of effective bioremediation strategies. Marine bacteria producing biosurfactants are promising agents for bio-remediating oil pollution in marine environments, making them prospective candidates for enhancing oil recovery. Molecular omics technologies are considered an emerging field of research in ecological and diversity assessment owing to their utility in environmental surveillance and bioremediation of polluted sites. A thorough literature review was undertaken to understand the applicability of different omic techniques used for bioremediation assessment using marine bacteria. This review further establishes that for bioremediation of environmental pollutants (i.e. heavy metals, hydrocarbons, xenobiotic and numerous recalcitrant compounds), organisms isolated from marine environments can be better used for their removal. The literature survey shows that omics approaches can provide exemplary knowledge about microbial communities and their role in the bioremediation of environmental pollutants. This review centres on applications of marine bacteria in enhanced bioremediation, using the omics approaches that can be a vital biological contrivance in environmental monitoring to tackle environmental degradation. The paper aims to identify the gaps in investigations involving marine bacteria to help researchers, ecologists and decision-makers to develop a holistic understanding regarding their utility in bioremediation assessment.

Biomimetic facile synthesis of zinc oxide and copper oxide nanoparticles from Elaeagnus indica for enhanced photocatalytic activity.

The present study focused on synthesizing ZnO nanoparticles (NPs) and CuO NPs using Elaeagnus indica leaf extract as reducing and stabilizing agents using Zn(O2CCH3)2 and Cu2SO4, respectively, for the first time. We have confirmed the formation of aggregated ZnO NPs and CuO NPs with phytochemicals by various spectral analyses and electron microscopy studies. The size of synthesized ZnO NPs and CuO NPs were in the range of 20-30 nm and 30-40 nm, respectively. The antimicrobial activity of ZnO NPs at 75 µg concentration is superior against Salmonella typhimurium, Klebsiella pneumonia, Bacillus subtilis, Staphylococcus epidermidis, and Aspergillus niger. While CuO nanoparticles with 75 µg concentration effectively inhibited S. typhimurium, B. subtilis, S. epidermidis, and A. niger. Phytochemicals and reactive oxygen species generated by the prepared NPs may account for the antimicrobial effects observed. The photodegradation of methylene blue by ZnO NPs and CuO NPs was 91% and 76%, respectively, for 6 h of sunlight exposure. CuO NPs and ZnO NPs have different intrinsic properties and phytochemical compositions; hence ZnO NPs photodegrade faster than CuO NPs even though ZnO has higher bandgap energy than CuO. Consequently, CuO and ZnO NPs produced from E. indica leaf extract might be utilized as antimicrobials and photocatalysts in the future.

Effect of excess activated sludge on vermicomposting of fruit and vegetable waste by using novel vermireactor.

This study aimed to clarify the effect of excess activated sludge (EAS) on vermicomposting of fruit and vegetable wastes (FVW). For this, a novel vermireactor consists of substrate and bed compartments was used for treating five types of FVW (banana peels, cabbage, lettuce, carrot, and potato) with and without the addition of EAS by earthworms. The EAS promoted the growth and cocoon production of earthworms, and the decomposition efficiency of FVW. The changes of dehydrogenase activity revealed that the EAS enhanced the microbial activity in all treatments except for the carrot. The organic matter content, total carbon and the C/N ratio showed a significant decrease after addition of EAS into FVW. The content of nitrogen and phosphorus was also improved in the final products after vermicomposting. This study suggested that the addition of EAS could be a feasible option to enhance the vermicomposting of FVW.

Vermistabilization of sugar beet (Beta vulgaris L) waste produced from sugar factory using earthworm Eisenia fetida: Genotoxic assessment by Allium cepa test.

In the present study, sugar beet mud (SBM) and pulp (SBP) produced as a waste by-products of the sugar industry were mixed with cattle dung (CD) at different ratios on dry weight basis for vermicomposting with Eisenia fetida. Minimum mortality and highest population of worms were observed in 20:80 (SBM20) mixture of SBM and 10:90 (SBP10) ratios. However, increased percentages of wastes significantly affected the growth and fecundity of worms. Nutrients like nitrogen, phosphorus, sodium, increased from initial feed mixture to final products (i.e., vermicompost), while organic carbon (OC), C:N ratio and electrical conductivity (EC) declined in all the products of vermicomposting. Although there was an increase in the contents of all the heavy metals except copper, chromium, and iron in SBM, the contents were less than the international standards for compost which indicates that the vermicompost can be used in the fields without any ill effects on the soil. Allium cepa root chromosomal aberration assay was used to evaluate the genotoxicity of pre- and post-vermicomposted SBM to understand the effect of vermicomposting on the reduction of toxicity. Genotoxicity analysis of post-vermicomposted samples of SBM revealed 18-75% decline in the aberration frequencies. Scanning electron microscopy (SEM) was recorded to identify the changes in texture in the control and vermicomposted samples. The vermicomposted mixtures in the presence of earthworms confirm more numerous surface irregularities that prove to be good manure.

Genotoxic assessment and optimization of pressmud with the help of exotic earthworm Eisenia fetida.

Genotoxicity of pressmud (PM) to Allium cepa was investigated to assess its toxic potential and to elucidate the effect of vermicomposting to reduce its toxicity. The PM produced as a waste by product of the sugar cane industry was mixed with cow dung (CD) at different ratios of 0:100 (V0), 25:75 (V25), 50:50 (V50), 75:25 (V75) and 100:0 (V100) (PM:CD) on a dry weight basis for vermicomposting with Eisenia fetida. Different concentrations of 100% PM sludge extract (10%, 20%, 40%, 60%, 80% and 100%) and negative control (distilled water) and positive control (maleic hydrazide) were analyzed with A. cepa assay to evaluate frequency of chromosomal aberrations before and after vermicomposting. Percent aberration was greatest (30.8%) after exposure to 100% PM extract after 6 h but was reduced to 20.3% after vermicomposting. Exposure to the extract induced c-mitosis, delayed anaphase, laggards, stickiness and vagrant aberrations. Microscopic examination of root meristem exposed to PM sludge extract showed significant inhibition of mitotic index. Also, the mitotic index decreased with increase in concentration of PM sludge extract. After vermicomposting the mitotic index was increased. However, increasing percentages of PM significantly affected the growth and fecundity of the worms and maximum population size was reached in the 25:75 (PM:CD) feed mixture. Nitrogen, phosphorus, sodium, electrical conductivity (EC) and pH increased from initial feed mixture to the final products (i.e., vermicompost), while organic carbon, C/N ratio and potassium declined in all products of vermicomposting. Scanning electron microscopy (SEM) was recorded to identify the changes in texture with numerous surface irregularities and high porosity that proves to be good vermicompost manure. It could be concluded that vermicomposting could be an important tool to reduce the toxicity of PM as evidenced by the results of genotoxicity.