Microbial fuel cells (MFCs) are emerging as a promising future technology for a wide range of applications in addition to sustainable electricity generation. Electroactive (EA) biofilms produced by microorganisms are the key players in the bioelectrochemical systems involving microorganism mediated electrocatalytic reactions. Therefore, genetically modifying the organism for increased production of EA biofilms and improving the extra electron transfer (EET) mechanisms may attribute to increase in current density of a MFC and an increased COD removal in wastewater treatment plant coupled MFC systems. Extracellular polysaccharides (EPS) produced by the organisms attribute to both biofilm formation and electron transfer. Although cell surface modification, media optimization and operation parameters validation are established as enhancement strategies for a fuel cell performance, engineering the vital genes involved in electroactive biofilm formation is the future hope. Therefore, in this review we critically address the biofilm formation mechanisms in electro active microorganisms, strategies for improving the biofilm formation leading to improved electrocatalytic rates for applications in bioelectrochemical systems.

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Glutaminase free l-asparaginase from a marine isolate Bacillus tequilensis PV9W: production, purification, characterization and its biological applications.

L-asparaginase, a therapeutic involved in cancer therapy, from Bacillus tequilensis PV9W (ansA gene) was cloned and over expressed in Escherichia coli BL21 (DE3), achieved the aim of maximizing the yield of the recombinant enzyme (6.02 ± 1.77 IU/mL) within 12 h. The native L-asparaginase of B. tequilensis PV9W was encapsulated using solid lipid particles by hot lipid emulsion method, which is reported for first time in this study. Subsequently, the lipid encapsulated L-asparaginase (LPE) was characterized by SEM, UV-Vis spectroscopy, FT-IR, SDS-PAGE and its thermo stability was also analyzed by TGA. Further characterization of LPE revealed that enzyme was highly stable for 25 days when stored at 25 °C, showed high pH (9) tolerance and longer trypsin half-life (120 min). In addition, the cytotoxic ability of LPE on HeLa cells was highly enhanced compared to the native L-asparaginase from Bacillus tequilensis PV9W. Moreover, better kinetic velocity and lower Km values of LPE aided to detect L-asparagine in cell extracts by Differential Pulse Voltammetry (DPV) method. The LPE preparation also showed least immunogenic reaction when tested on normal macrophage cell lines. This LPE preparation might thus pave way for efficient drug delivery and enhancing the stability of L-asparaginase for its therapeutic applications.

Glutaminase free L-asparaginase is a vital enzyme because of its anti cancer potential. A potent bacterium isolated from marine environment, producing glutaminase free L-asparaginase using M-9 medium with L-10 asparagine was identified as Pseudomonas plecoglossicida RS1 by 16S rRNA gene sequencing. Statistical modeling was employed to optimize the medium using sugar cane industry effluent as a sole substrate for L-asparaginase production. The enzyme activity of L-asparaginase was increased with M-9 medium containing 0.8% effluent (3.25 ± 0.12 IU/mL) than M-9 medium containing 0.3% L-asparagine (0.73 ± 0.08IU/mL). The apparent K m and V max of the purified L-asparaginase was 2.25 ± 0.61 mM and 15 8.9 ± 0.81 IU/mL/min respectively and the optimal activity of L-asparaginase was at pH 8.5 and 55ºC.