Microbial cellulases are the enzymes widely studied due to their enormous applications in biochemical industry. Among 12 fungal isolates isolated from mangrove plant debris and soil sample collected from Valanthakad Mangroves, Kerala, India, 3 of them were found to exhibit cellulolytic activity. Among them, the most potent isolate which exhibited maximum cellulolytic activity was identified as Trichoderma viride VKF3 [Gene bank accession number- JX683684.1] based on colony morphology, microscopic observation and molecular centeracterization using D1/D2 region amplification. The isolate T. viride VKF3 was found to be non-phytopathogenic against the selected plants. Neighbour joining tree depicted its least divergence rate from the root taxon HM466686.1. T. viride VKF3 was grown under dynamic carbon, nitrogen sources, pH and temperature of the medium to draw out the optimum conditions for cellulase production. Protein stability kinetics and biomass production was also studied upto 11th day of incubation. It was evident from the study, that dextrose and beef extract could be used as major carbon and nitrogen sources in submerged fermentation at pH 9.0 and incubation temperature of 25°C to get maximum CMCase yield. Optimum enzyme recovery period was identified between 5th to 9th days of incubation beyond which the enzyme activity was reduced. By comparing two fermentation methods, submerged fermentation was found to be the best for maximum enzyme production. But utilization of substrates like sugarcane bagasse and cassava starch waste in the SSF offers a better scope in biodegradation of solid waste contributing to solid waste management.
According to the United Nations Environment Programme (UNEP), soil health is declining over the decades and it has an adverse impact on human health and food security. Hence, soil health restoration is a need of the hour. It is known that microorganisms play a vital role in remediation of soil pollutants like heavy metals, pesticides, hydrocarbons, etc. However, the indigenous microbes have a limited capacity to degrade these pollutants and it will be a slow process. Genetically modified organisms (GMOs) can catalyze the degradation process as their altered metabolic pathways lead to hypersecretions of various biomolecules that favor the bioremediation process. This review provides an overview on the application of bioengineered microorganisms for the restoration of soil health by degradation of various pollutants. It also sheds light on the challenges of using GMOs in environmental application as their introduction may affect the normal microbial community in soil. Since soil health also refers to the potential of native organisms to survive, the possible changes in the native microbial community with the introduction of GMOs are also discussed. Finally, the future prospects of using bioengineered microorganisms in environmental engineering applications to make the soil fertile and healthy have been deciphered. With the alarming rates of soil health loss, the treatment of soil and soil health restoration need to be fastened to a greater pace and the combinatorial efforts unifying GMOs, plant growth-promoting rhizobacteria, and other soil amendments will provide an effective solution to soil heath restoration ten years ahead.
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