Inactivation of polygalacturonase and pectate lyase produced by pH tolerant fungus Fusarium moniliforme NCIM 1276 in a liquid medium and in the host tissue

Chemometric study on the biochemical marker of the manglicolous fungi to illustrate its potentiality as a bio indicator for heavy metal pollution in Indian Sundarbans

The study represents in vitro chemometric approach for assessing the heavy metal pollution in Indian Sundarbans. Physio-chemical and elemental characterisation of the sediment samples of Indian Sundarbans had shown high enrichments of toxic metal ions. It was characterised by elevated enrichment factors (2.16-10.12), geo-accumulation indices (0.03 -1.21), contamination factors (0.7-3.43) and pollution load indices (1.0-1.25) which showed progressive sediment quality deterioration and ecotoxicological risk due to metal ions contamination. The physio-chemical parameters of the sediments were replicated and computational chemometric modeling was utilized to assess fungal metabolic growth. All the fungi isolates had shown maximum metabolic activity in high temperature, alkaline pH, and high salinity. Further, the fungal metabolic activity was assessed in different gradient of heavy metal concentration. The significant deterioration of biochemical marker with increasing concentration of heavy metal indicates the status of the microbial health due to toxic metal pollution in the mangrove habitat.

Rye Snow Mold-Associated Microdochium nivale Strains Inhabiting a Common Area: Variability in Genetics, Morphotype, Extracellular Enzymatic Activities, and Virulence

Snow mold is a severe plant disease caused by psychrophilic or psychrotolerant fungi, of which Microdochium species are the most harmful. A clear understanding of Microdochium biology has many gaps; the pathocomplex and its dynamic are poorly characterized, virulence factors are unknown, genome sequences are not available, and the criteria of plant snow mold resistance are not elucidated. Our study aimed to identify comprehensive characteristics of a local community of snow mold-causing Microdochium species colonizing a particular crop culture. By using the next-generation sequencing (NGS) technique, we characterized fungal and bacterial communities of pink snow mold-affected winter rye (Secale cereale) plants within a given geographical location shortly after snowmelt. Twenty-one strains of M. nivale were isolated, classified on the basis of internal transcribed spacer 2 (ITS2) region, and characterized by morphology, synthesis of extracellular enzymes, and virulence. Several types of extracellular enzymatic activities, the level of which had no correlations with the degree of virulence, were revealed for Microdochium species for the first time. Our study shows that genetically and phenotypically diverse M. nivale strains simultaneously colonize winter rye plants within a common area, and each strain is likely to utilize its own, unique strategy to cause the disease using "a personal" pattern of extracellular enzymes.

Biotechnology Potential of Marine Fungi Degrading Plant and Algae Polymeric Substrates

Filamentous fungi possess the metabolic capacity to degrade environment organic matter, much of which is the plant and algae material enriched with the cell wall carbohydrates and polyphenol complexes that frequently can be assimilated by only marine fungi. As the most renewable energy feedstock on the Earth, the plant or algae polymeric substrates induce an expression of microbial extracellular enzymes that catalyze their cleaving up to the component sugars. However, the question of what the marine fungi contributes to the plant and algae material biotransformation processes has yet to be highlighted sufficiently. In this review, we summarized the potential of marine fungi alternatively to terrestrial fungi to produce the biotechnologically valuable extracellular enzymes in response to the plant and macroalgae polymeric substrates as sources of carbon for their bioconversion used for industries and bioremediation.

In vitro oral processing of raw tomato: Novel insights into the role of endogenous fruit enzymes

During consumption of fruits, the breakdown of the fruit tissue due to oral processing (chewing, mixing with saliva) may activate or increase the rate of endogenous enzyme activities via the disruption of the cell wall, cellular decompartmentalization, and particle size reduction allowing the enzymes to reach their substrates. The aim of this study was to investigate the activity of one such endogenous fruit enzyme (pectin methylesterase [PME] [E.C. 3.1.1.11]) during in vitro oral processing of raw tomatoes and associated changes in viscosity and microstructure. Oral processing of tomatoes purees was examined in the presence of artificial saliva (AS) at 37°C. in vitro oral processing was followed using immunofluorescence microscopy, apparent viscosity measurements, spectrophotometric, and titrimetric techniques. The results demonstrated that PME had slight but significant activity in the tomato fruit during in vitro oral processing generating methanol as a function of oral processing time, which was further evidenced using immunolabeling techniques to detect methylated pectin epitopes. A significant shear-thinning behavior of the tomato puree was observed due to dilution and/or endogenous fruit enzyme activity. These results suggest that activity of other fruit enzymes, such as polygalacturonase, which catalyzed the depolymerization of unmethylated pectin chains, might have resulted in a decrease in viscosity, which compensated for the increased potential for gel formation (if any) caused by PME. These interesting insights into the role of endogenous fruit enzymes might pave the way to the understanding of fruit viscosity modification occurring in the mouth and help in rational design of new fruit-based products.

Characterization and molecular modeling of polygalacturonase isoforms from Saccharomyces cerevisiae

Earlier, low-temperature-active polygalacturonase isoforms from Saccharomyces cerevisiae PVK4 were isolated and purified. Substrate specificity of polygalacturonase isoforms indicated high affinity for pectins and very low enzyme activity towards non-pectic polysaccharides. To characterize the polygalacturonase isoforms, biochemical, spectral, and in silico approaches were used. The apparent K_m and V_max values for hydrolysis of pectin and galacturonic acid were 0.31 mg/ml and 3.15 mmol min/mg, respectively. Interestingly, the polygalacturonase isoforms were found to be more stable at optimal pH and temperature of 4.5 and 40 °C, respectively. These isoforms were reacted with different metal ions; Cd²⁺ and Ni²⁺ severely inhibited the enzyme activity, while Mg²⁺, Zn²⁺, Cd²⁺, Fe²⁺ Cu²⁺, and Ni²⁺ inhibited to a lesser extent, which clearly demonstrated that variations in enzyme activity were due to their differential binding affinity of metal ions. Furthermore, decrease in the viscosity of polygalacturonic acid and citrus pectin by these isoforms was approximately four and six times higher than the rate of release of reducing sugars. This indicates that polygalacturonase isoforms have an endo-mode of action. In addition to the above, thermostability of purified polygalacturonase isoforms was studied by circular dichroism and fluorescence spectroscopy. Circular dichroism showed 18% alpha helix and 57% beta sheets at pH 5, while at pH 7, 8, and 9 there was an increase of random coil. Fluorescence studies revealed small conformational changes, which were observed at 30-50 °C, while unfolding transition region was noticed between 60 and 70 °C. The purified enzyme fractions were analyzed by MALDI-TOF MS. Finally, 3D model structures for isoenzymes of polygalacturonase of S. cerevisiae were generated and validated as good quality models, which are also suitable for molecular interaction studies.