Microbial pectinolytic enzymes: A review

Extracellular polymeric substances (EPS) produced by microorganisms are a complex mixture of biopolymers primarily consisting of polysaccharides, as well as proteins, nucleic acids, lipids and humic substances. EPS make up the intercellular space of microbial aggregates and form the structure and architecture of the biofilm matrix. The key functions of EPS comprise the mediation of the initial attachment of cells to different substrata and protection against environmental stress and dehydration. The aim of this review is to present a summary of the current status of the research into the role of EPS in bacterial attachment followed by biofilm formation. The latter has a profound impact on an array of biomedical, biotechnology and industrial fields including pharmaceutical and surgical applications, food engineering, bioremediation and biohydrometallurgy. The diverse structural variations of EPS produced by bacteria of different taxonomic lineages, together with examples of biotechnological applications, are discussed. Finally, a range of novel techniques that can be used in studies involving biofilm-specific polysaccharides is discussed.

https://www.mdpi.com/1420-3049/14/7/2535/pdf

Bacterial extracellular polysaccharides involved in biofilm formation.

https://www.cell.com/trends/neurosciences/pdf/S0166-2236(08)00163-X.pdf

Neuronal calcium mishandling and the pathogenesis of Alzheimer's disease.

Phosphatidylserine (PS) is the most abundant negatively charged phospholipid in eukaryotic membranes. PS directs the binding of proteins that bear C2 or gamma-carboxyglutamic domains and contributes to the electrostatic association of polycationic ligands with cellular membranes. Rather than being evenly distributed, PS is found preferentially in the inner leaflet of the plasma membrane and in endocytic membranes. The loss of PS asymmetry is an early indicator of apoptosis and serves as a signal to initiate blood clotting. This review discusses the determinants and functional implications of the subcellular distribution and membrane topology of PS.

The distribution and function of phosphatidylserine in cellular membranes.

Autoimmunity and the Clearance of Dead Cells

The stability of Debaryomyces nepalensis NCYC 3413 xylose reductase, a homodimeric enzyme recombinantly expressed and purified from E. coli Rosetta cells, was studied at different pH ranging from 5.0 to 10.0. Deactivation kinetics at different pH were studied by analyzing residual activity of the recombinant enzyme over time at 40 °C whereas conformational changes and stability dependence were investigated by using circular dichroism and differential scanning calorimetry. Four osmolytes viz. glycerol, sucrose, trehalose and sorbitol were explored for their effect on the deactivation and melting temperatures of the enzyme under neutral and extreme pH conditions. The enzyme was found to be catalytically and structurally stable at pH 7.0 with half-life of 250 min and a melting temperature of 50 °C. It was found that alteration in both secondary and tertiary structures caused enzyme deactivation in acidic pH while increased deactivation rates at alkaline pH was attributed to the variation of tertiary structure over time. Estimated thermodynamic parameters also showed that the enzyme stability was highest at neutral pH with ΔH of 348 kcal/mole and ΔG40 of 9.53 kcal/mole. All four osmolytes were effective in enhancing enzyme stability by several folds at extreme pH with sorbitol being the most efficient, which increased enzyme half-life by 11-fold at pH 10.0 and 8-fold at pH 5.0.

Counteraction of osmolytes on pH-induced unfolding of xylose reductase from Debaryomyces nepalensis NCYC 3413

Numerical Investigation on Low Salinity Augmented Microbial Flooding LSAMF within a Sandstone Core for Enhanced Oil Recovery Under Nonisothermal and Fluctuating pH Conditions

BACKGROUND Physical parameters like pH and temperature play a major role in the design of an industrial enzymatic process. Enzyme stability and activity are greatly influenced by these parameters; hence optimization and control of these parameters becomes a key point in determining the economic feasibility of the process. OBJECTIVE This study was taken up with the objective to optimize physical parameters for maximum stability and activity of xylose reductase from D. nepalensis NCYC 3413 through separate and simultaneous optimization studies and comparison thereof. METHODS Effects of pH and temperature on the activity and stability of xylose reductase from Debaryomyces nepalensis NCYC 3413 were investigated by enzyme assays and independent variables were optimised using surface response methodology. Enzyme activity and stability were optimised separately and concurrently to decipher the appropriate conditions. RESULTS Optimized conditions of pH and temperature for xylose reductase activity were determined to be 7.1 and 27 °C respectively, with predicted responses of specific activity (72.3 U/mg) and half-life time (566 min). The experimental values (specific activity 50.2 U/mg, half-life time 818 min) were on par with predicted values indicating the significance of the model. CONCLUSION Simultaneous optimization of xylose reductase activity and stability using statistical methods is effective as compared to optimisation of the parameters separately.

Simultaneous Optimization of Activity and Stability of Xylose Reductase from D. nepalensis NCYC 3413 Using Statistical Experimental Design.

Cyclic β-glucans have ring-like structures with varying degree of polymerization. The size of the rings produced by bacteria vary from 13 to 25 glucose residues and are substituted with different functional groups, including phosphoglycerol, phosphoethanolamine, succinyl, methylmalonyl, and acetyl. Phosphorylase catalyzes the degree of polymerization. Four types of cyclic glucans are found in prokaryotes namely cyclic β-(1,2), β-(1,3)-(1,6), β-(1,3) and β-(1,6)-(1,3) glucans. The β-glucan binds to the receptor, dectin-1 and induces antimicrobial, anti-inflammatory, innate, and adaptive immunity. They exhibit good biocompatibility against human embryonic kidney 293 cells.

Properties of Cyclic Glucans

Microbial fuel cells (MFCs) have great potential in sustainable energy production, treating waste, and reducing CO 2 emissions. The paradigm shift brought about by the discovery of electrochemically active bacteria that directly transfer electrons without exogenous mediators and the development of MFC architecture with low-cost components (e.g., electrodes, membranes) has boosted the power density over 1 kW/m 3 (reactor volume) and long-term stability at the laboratory scale. However, the MFC technology is yet to be commercially exploited for different applications because several of its drawbacks are yet to be resolved. This chapter deals with recent advances in the MFC architecture, including individual components, and the problems associated with the different parameters that affect the operational performance besides concerns regarding the scale-up criteria. Lastly, the SWOT analysis has been performed for MFC commercialization to evaluate competitiveness and aid strategic planning. 

Sathyanarayana N. Gummadi

Papers

Counteraction of osmolytes on pH-induced unfolding of xylose reductase from Debaryomyces nepalensis NCYC 3413

Numerical Investigation on Low Salinity Augmented Microbial Flooding LSAMF within a Sandstone Core for Enhanced Oil Recovery Under Nonisothermal and Fluctuating pH Conditions

Simultaneous Optimization of Activity and Stability of Xylose Reductase from D. nepalensis NCYC 3413 Using Statistical Experimental Design.

Properties of Cyclic Glucans

Scaling up and applications of microbial fuel cells