Bhavtosh A. Kikani

The present study proposes an integrated approach using a novel cyanobacterial-bacterial co-culture consisting of Desertifilum tharense MASKD1 and bacterial consortium DBPS1 to treat secondary sewage effluent in a raceway pond (50 L). Noticeably, the synergistic growth was achieved in the undiluted secondary sewage effluent without supplementation of any nutrients. The cyanobacterial-bacterial co-culture system achieved an improved tertiary sewage treatment as compared to the use of individual cultures. The Liquid Chromatography-High Resolution Mass Spectrometry (LC-HRMS) analysis confirmed an efficient removal of multiple ECs. The 16S rRNA gene amplicon sequencing explained how the co-culture community dynamics might have contributed in the bioremediation process. The harvested biomass was further valorized for the recovery of phycocyanin by ammonium sulphate fractionation followed by size exclusion chromatography. The antioxidant activity of phycocyanin was evaluated by Caenorhabditis elegans lifespan assays. The median survival duration of C. elegans was 14 days, which increased 1.64 times (to 23 days) in the presence of phycocyanin. In addition, the catalase activity assay in C. elegans further supported this observation. The catalase activity decreased by 20 Units/mg in worms treated with H₂O₂ along with phycocyanin compared to those treated with H₂O₂ alone. This reduction might be attributed to the direct scavenging of ROS or the decreased intracellular accumulation of H₂O₂ in the presence of phycocyanin. The studied cyanobacterium accumulated significant neutral lipid under nitrogen starvation, indicating its possible use as a biodiesel. Additionally, the findings supported the concept of a self-sustainable electrode design, wherein treated wastewater was innovatively utilized as the electrolyte in a Ni-fabric–based electrochemical cell. The green hydrogen and oxygen produced were comparable to the previous reports. Thus, this study demonstrates an interdisciplinary bio-electrochemical strategy by integrating wastewater remediation, bioproduct synthesis and renewable energy generation. Graphical abstract

Microbial amylases should essentially remain active at higher temperatures, and in the alkaline pH and a range of surfactants to be suitable as detergent additives. In the present study, a thermophilic amylase producing bacterium, Bacillus licheniformis UDS-5 was isolated from Unai hot water spring in Gujarat, India. It was identified as a potent amylase producer during starch plate-based screening process. Therefore, the physicochemical parameters influencing amylase production were optimized using Plackett–Burman design and Central Composite Design. The amylase was purified through ammonium sulfate precipitation, size exclusion and ion exchange chromatography, achieving the purification fold and yield to be 9.2 and 40.6%, respectively. The enzyme displayed robust stability and activity across a wide range of temperatures and pHs, with an increased half-life and reduced deactivation rate constant. The amylase exhibited optimal catalysis at 70 °C and pH 8. The kinetic studies revealed Km and Vmax values of 0.58 mg/mL and 2528 μmol/mL/min, respectively. Besides, the purified amylase displayed stability in the presence of various metal ions, surfactants, and chelators suggesting its potential for industrial applications, particularly in the detergent industry. Moreover, detergent application studies demonstrated its efficacy in enhancing washing performance. A comparative profile on washing efficiency of the studied amylase and the commercial amylase with various detergents pointed towards its possible future use as a detergent additive.

A thermostable l-asparaginase was produced from Bacillus licheniformis UDS-5 (GenBank accession number, OP117154). The production conditions were optimized by the Plackett Burman method, followed by the Box Behnken method, where the enzyme production was enhanced up to fourfold. It secreted l-asparaginase optimally in the medium, pH 7, containing 0.5% (w/v) peptone, 1% (w/v) sodium chloride, 0.15% (w/v) beef extract, 0.15% (w/v) yeast extract, 3% (w/v) l-asparagine at 50 °C for 96 h. The enzyme, with a molecular weight of 85 kDa, was purified by ion exchange chromatography and size exclusion chromatography with better purification fold and percent yield. It displayed optimal catalysis at 70 °C in 20 mM Tris–Cl buffer, pH 8. The purified enzyme also exhibited significant salt tolerance too, making it a suitable candidate for the food application. The l-asparaginase was employed at different doses to evaluate its ability to mitigate acrylamide, while preparing French fries without any prior treatment. The salient attributes of B. licheniformis UDS-5 l-asparaginase, such as greater thermal stability, salt stability and acrylamide reduction in starchy foods, highlights its possible application in the food industry.

Casein decorated silicainfused magnetite (Fe₃O₄‐SiO₂) nanoparticles are employed to immobilize commercial α‐amylase, where glutaraldehyde serves as a cross linker. The optimal concentration of variables, such as casein (1.4%w/v), Fe₃O₄‐SiO₂ (106 µl), glutaraldehyde (55µl) and amylase (1 mg/ml) are defined by a Box Behnken design. The binding of casein, glutaraldehyde and enzyme over the nanoparticles are further confirmed structurally by fourier transform infrared spectroscopy (FTIR) and thermal gravimetric analysis (TGA). The loading capacity is 37 µg amylase over 1 µg of silica infused magnetite nanoparticles. The optimum pH for the catalysis of soluble and immobilized amylases is the same, i.e. pH 7. However, the pH range for catalysis is improved upon immobilization. The temperature optimum of soluble and immobilized amylases are 40 and 70 °C, respectively. The amylase stability is improved upon immobilization, as shown by enhanced half‐life and reduced deactivation rate constant. The immobilized amylase is used for 17 consecutive cycles with retention of 52% of the residual activity. The immobilized amylase produces high maltose syrup using the industrial wastewater containing corn starch. The ISO 5377 protocol determines dextrose equivalence values to be 36% and 24% during cycle 1 and cycle 2, respectively. The findings point out its possible commercial use.

Microbial enzymes have contributed significantly to the development of biotech based industries over the recent past. Importantly, the microbial α‐amylases share a major market along with proteases. Starch gets hydrolyzed to dextrin, maltotetroses, maltotrioses, maltose, and glucose in trace amount using amylases. To be suitable commercially, the amylase should be stable at higher temperatures and a wide range of pH values. Moreover, it should also exhibit resistance against a range of chelators, surfactants, and denaturants. It is quite strenuous to isolate an amylase harboring all the required qualities. Therefore, various strategies have been employed to achieve the required attributes. In the present mini‐review, amylase immobilization on conventional matrices as well as on different types of nanomaterials has been discussed with a special emphasis on improvement in the stability and reusability. The stability of the nanomaterials against various physical, chemical, and biological stress is a key factor to be explored commercially. The mini‐review includes mainly magnetite, non‐magnetite, and hybrid (organic–inorganic) nanomaterials. Conclusively, it is anticipated that the advanced strategies would help to overcome the technical barriers in the industrial sectors for better continuous applications of microbial amylases.

Amylases hydrolyze starch to diverse products including dextrins and progressively smaller polymers of glucose units. Thermally stable amylases account for nearly 25% of the enzyme market. This review highlights the structural attributes of the α-amylases from thermophilic bacteria. Heterologous expression of amylases in suitable hosts is discussed in detail. Further, specific value maximization approaches, such as protein engineering and immobilization of the amylases are discussed in order to improve its suitability for varied applications on a commercial scale. The review also takes into account of the immobilization of the amylases on nanomaterials to increase the stability and reusability of the enzymes. The function-based metagenomics would provide opportunities for searching amylases with novel characteristics. The review is expected to explore novel amylases for future potential applications.