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Genetic Engineering and Fabrication of Microbial Cell System for Biohydrogen Production
Published in Sonil Nanda, Prakash K. Sarangi, Biohydrogen, 2022
Sushma Chauhan, Balasubramanian Velramar, Rakesh Kumar Soni, Mohit Mishra, Vargobi Mukherjee, Tanushree Baldeo Madavi, Sudheer D.V.N. Pamidimarri
Masukawa et al. (2007) generated a series of mutants, which cannot fix the nitrogen by Anabaena sp. 7120. The recombinant cells carrying mutation ΔHup, ΔNifV1 resulted in a higher rate of H2 production in the presence of N2. Though the gene accessory proteins for the nitrogen fixation can diminish the nitrogenase activity, the substitution of amino acids in the active center can lead to the loss of activity without disturbing the hydrogen production by nitrogenase. Amino acid replacement of Azotobacter vinelandii nitrogenase catalytic center eliminated N2 fixation and allowed better proton reduction, helped in more H2 production in the presence of N2, and the aerobic environment in the case of cyanobacteria. Likewise, several variants generated by amino acid replacements in the catalytic site of nitrogenase in Anabaena exhibited the increased levels of H2 production compared to the reference strains in the presence of N2 (Masukawa et al., 2010).
Secondary Clarification of Wastewater Relying on Biological Treatment Processes: Advancements and Drawbacks
Published in Maulin P. Shah, Wastewater Treatment, 2022
Vijayaraghavan et al. (2007) investigated palm oil mill effluent aerobic treatment utilizing an activated sludge process. Efficiency of the process was evaluated by treating anaerobic digest of raw palm oil mill effluent and adjusting hydraulic retention time. COD was reported to efficiently decrease to around 98% post 60 hours of retention time. Zhu and Chen (2011) presented an efficient biological wastewater treatment strategy for reducing nitric oxide (NO) and nitrous oxide (N2O) production to 50% and 68.7%, respectively, during anaerobic-aerobic processes. Sludge alkaline fermentation slurry was utilized as the carbon source in synthetic wastewater, irrespective of the commonly used acetic acid. The report suggested the feasibility of utilizing sludge fermentation liquid for treatment of municipal wastewater. Also, this technique caters to a lower energy requirement for yielding efficient performance. Treatment of semiconductor industry dimethyl sulfoxide (DMSO)-enriched wastewater by direct activated sludge biological treatment was reported to be a feasible option, significantly reducing the input cost (Park et al., 2001). Ji et al. (2010) enhanced the biological activated sludge wastewater treatment process by studying variations in biodegradation duration, operating temperature, magnetic density, and medium pH. The effect of the magnetic field was regarded as the most important factor boosting efficiency of treatment. Kargi and Özmıhçı (2002) offered an alternative method for treating nitrogen-deficient wastewater by supplementing activated sludge reactors with Azotobacter vinelandii, the nitrogen-fixing bacteria. The method aimed at reducing the cost of nitrogenous compounds that are routinely used for efficient treatment of wastewaters deficient in nitrogen.
Biodegradation of cyanide in cassava wastewater using a novel thermodynamically-stable immobilized rhodanese
Published in Preparative Biochemistry & Biotechnology, 2021
Adedeji Nelson Ademakinwa, Mayowa Oladele Agunbiade, Oladapo Fagbohun
The enzymes mostly involved in the biodegradation of cyanide are nitrilase and rhodanese with the latter being the most evolved in terms of cyanide detoxification.[8,9] Rhodaneses (thiosulfate: cyanide sulphurtransferase; EC 2.8.1.1) are ubiquitous enzymes that catalyze the transfer of sulfur from thiosulfate to cyanide with the subsequent production of a less toxic product (thiocyanate). Rhodanese is highly ubiquitous as it has been found in several plant and animal species.[10] Several purification strategies have been employed for rhodanese which includes chromatographic separation, ultrafiltration, etc.[7,8,10] These methods are often laborious, time-consuming and expensive considering the fact that the enzyme is to be deployed for industrial use such as in the treatment of cyanide-contaminated wastewater.[11] Several authors have utilized bacteria such as Escherichia coli,[12]Azotobacter vinelandii,[13]Bacillus pumilus[3] and rhodanese[9] in the biodegradation of cyanide. It can be concluded from these studies that both microorganisms and enzymes offer an eco-friendly route to cyanide detoxification in comparison with the physical/chemical techniques.