Sunil H. Koli

Antimicrobial activity of prodigiosin is attributable to plasma-membrane damage

Abstract The bacterial pigment prodigiosin has various biological activities; it is, for instance, an effective antimicrobial. Here, we investigate the primary site targeted by prodigiosin, using the cells of microbial pathogens of humans as model systems: Candida albicans, Escherichia coli, Staphylococcus aureus. Inhibitory concentrations of prodigiosin; leakage of intracellular K+ ions, amino acids, proteins and sugars; impacts on activities of proteases, catalases and oxidases; and changes in surface appearance of pathogen cells were determined. Prodigiosin was highly inhibitory (30% growth rate reduction of C. albicans, E. coli, S. aureus at 0.3, 100 and 0.18 μg ml−1, respectively); caused leakage of intracellular substances (most severe in S. aureus); was highly inhibitory to each enzyme; and caused changes to S. aureus indicative of cell-surface damage. Collectively, these findings suggest that prodigiosin, log Poctanol–water 5.16, is not a toxin but is a hydrophobic stressor able to disrupt the plasma membrane via a chaotropicity-mediated mode-of-action.

Fluconazole treatment enhances extracellular release of red pigments in the fungus Monascus purpureus

Abstract Traditional methods for the production of food grade pigments from the fungus Monascus spp. mostly rely on submerged fermentation. However, the cell‐bound nature and intracellular accumulation of pigments in Monascus spp. is a major hurdle in pigment production by submerged fermentation. The present study focused on the investigation of the effect of the antifungal agent fluconazole on red pigment production from Monascus purpureus (NMCC‐PF01). At the optimized concentration of fluconazole (30 &mgr;g ml−1), pigment production was found to be enhanced by 88% after 96 h and it remained constant even after further incubation up to 168 h. Ergosterol, a sterol specific to fungi, was also extracted and estimated as a function of fungal growth. The concentration of ergosterol in fluconazole‐treated fermentation broth was reduced by 49% as compared to control broth. Thus it could be responsible for facilitating the release of intracellular and cell‐bound pigments. Nevertheless, the role of cell transporters in transporting out the red pigments cannot be ignored and deserves further attention. Qualitative analysis of red pigment by thin layer chromatography, UV spectroscopy and mass spectrometric analysis (ESIMS) has confirmed the presence of the well‐known pigment rubropunctamine. In addition, this fermentation process produces citrinin‐free pigments. This novel approach will be useful to facilitate increased pigment production by the release of intracellular or cell‐bound Monascus pigments.

Prospective of Microbial Exopolysaccharide for Heavy Metal Exclusion

Metals as a resource are depleting, and on another side, it fetches serious environmental pollution causing a threat to human health and ecosystem. The heavy metal accumulation due to anthropogenic activities results in toxicological manifestation. The traditional methods of remediation are not cost effective, efficient, and ecofriendly which necessitate and motivate towards the safe, effective, and ecofriendly biological methods. The increasing presence of heavy metals in the microbial habitat compels the microbes to develop the ability to tolerate or resist the presence of heavy metals. Exopolysaccharide (EPS) production is one of the strategies of microbes to fight against metal stress. EPS is a microbial biopolymer which is generally produced under stress from harsh environment and nutrition conditions. EPSs are cell-associated or secreted outside the cell and comprised organic macromolecules such as polysaccharides, proteins, and phospholipids in addition to some non-polymeric molecules. EPSs work as competent biosorbents with an anionic reactant group that effectively sequesters cationic heavy metals by electrostatic interactions. The present paper summarizes the EPSs with its types, role, and biosynthesis and an endeavor to elucidate the interaction mechanism of EPSs with heavy metal with supportive and distinctive applications for heavy metal exclusion. The review concluded with the current challenges and future prospects to make the EPS an efficient biosorbent.

Effect of copper on probiotic properties of Lactobacillus helveticus CD6

Copper imparts better organoleptic properties to cheese, while cheese acts as a vehicle for probiotic cultures. These studies revealed that copper stress changed key probiotic properties like acid and bile salt tolerance of a model organism Lactobacillus helveticus CD6. After growing the culture in copper stress, the acid tolerance at pH 2 was lost along with a decrease in bile salt tolerance by 15%, while other desiring properties like auto-aggregation, cell surface hydrophobicity and antibacterial activity were improved. This study suggests that copper tolerant culture with retained probiotic properties could be used to deliver through cheese to the consumers.

Bacterial Cellulose-Based Hydrogels: Synthesis, Properties, and Applications

There is an importunate effort taking place worldwide to obtain the innovative hydrogels either from natural, synthetic, or mixed type polymers, ever since the breakthrough invention of the first hydrogel of polyhydroxy ethyl methacrylate. Predominantly the cellulose-based hydrogels attracted the attention of researchers due to its renewable, biodegradable biopolymeric nature. In comparison to plant cellulose (PC), the bacterial cellulose (BC) has been preferred due to its pure fibrous biomaterial nature, high crystallinity, ultrafine three-dimensional nanostructure network, high water absorption, superior mechanical properties, B. V. Mohite · S. H. Koli School of Life Sciences, North Maharashtra University, Jalgaon, Maharashtra, India S. V. Patil (*) School of Life Sciences, North Maharashtra University, Jalgaon, Maharashtra, India North Maharashtra Culture Collection Centre, North Maharashtra University, Jalgaon, Maharashtra, India e-mail: satish.patil7@gmail.com # Springer International Publishing AG, part of Springer Nature 2018 Md. I. H. Mondal (ed.), Cellulose-Based Superabsorbent Hydrogels, Polymers and Polymeric Composites: A Reference Series, https://doi.org/10.1007/978-3-319-76573-0_2-1 1 biocompatibility, and biodegradability. These promising valuable properties of BC exploit its use especially in hydrogel form in a variety of technological fields like a development of new bacterial cellulose-based hydrogels. The present review focused on its current synthesis methods and use in biomedicine, pharmaceutical, environment, agriculture, etc. In recent years BC itself and in combination have become the subject of intensive studies for the synthesis of hydrogels in search of properties and applications of BC-based hydrogels. On the whole, the review after introducing BC production and its properties discusses the synthesis of BC-based smart hydrogels with various composite materials, formation mechanism, and improved characters. The latest use of BC-based hydrogels in both well-established and innovative high-tech fields is emphatically reviewed. The review concludes with the need for future research with some suggestions for BC-based hydrogels to be commercialized as a smart biomaterial.

Phytosynthesized Gold Nanoparticles-Bacillus thuringiensis (Bt–GNP) Formulation: A Novel Photo Stable Preparation Against Mosquito Larvae

It is well-known that the sunlight irradiation damages the spores and toxin produced by Bacillus thuringiensis (Bt), which leads to loss of their insecticidal activity. This photodegradation problem is addressed in the present investigation by use of green phytosynthesized gold nanoparticles (GNP) as a photoprotectant. The efficiency of Bt with GNP before and after exposing to sunlight was evaluated against the larvae of Aedes aegypti and Anopheles subpictus. The bioassay results focused that after sunlight irradiation the Bt significantly lose their activity for Ae. aegypti (23.13%) and An. subpictus (27.08%). Although the individual GNP showed very less activity against tested larvae, it was observed that in combination with Bt it significantly enhances activity and consequently reduced the LC50 of Bt–GNP. Similarly, even after irradiation of Bt–GNP formulation, the enhanced activity was found against Ae. aegypti (23.10%) and An. subpictus (27.24%). Henceforth in the case of Bt–GNP formulation, the GNP it was not only protecting the Bt from sunlight but enhances its larvicidal potential. The interactions between the GNP and Bt toxin which might be the main reason to protect the Bt from sunlight and can help to locate the Bt toxin at the target site.

Heavy Metal Stress and Its Consequences on Exopolysaccharide (EPS)-Producing Pantoea agglomerans

AbstractCurrently, the heavy metal pollution is of grave concern, and the part of microorganism for metal bioremediation should take into account as an efficient and economic strategy. On this framework, the heavy metal stress consequences on exopolysaccharide (EPS)-producing agricultural isolate, Pantoea agglomerans, were studied. The EPS production is a protective response to stress to survive and grow in the metal-contaminated environment. P. agglomerans show tolerance and mucoid growth in the presence of heavy metals, i.e., mercury, copper, silver, arsenic, lead, chromium, and cadmium. EDX first confirmed the metal accumulation and further, FTIR determined the functional groups involved in metal binding. The ICP-AES identified the location of cell-bound and intracellular metal accumulation. Metal deposition on cell surface has released more Ca2+. The effect on bacterial morphology investigated with SEM and TEM revealed the sites of metal accumulation, as well as possible structural changes. Each heavy metal caused distinct change and accumulated on cell-bound EPS with some intracellular deposits. The metal stress caused a decrease in total protein content and increased in total carbohydrate with a boost in EPS. Thus, the performance of P. agglomerans under metal stress indicated a potential candidate for metal bioremediation. Graphical Abstractᅟ

Improved method for effective screening of ACC (1-aminocyclopropane-1-carboxylate) deaminase producing microorganisms

Aminocyclopropane-1-carboxylate deaminase (ACCD) producing microorganisms support plant growth under a variety of biotic and abiotic stress conditions such as drought, soil salinity, flooding, heavy metal pollution and phyto-pathogen attack. Available screening methods for ACCD give idea only about its primary microbial ACCD activity than the actual potential. In the present investigation, we have simply improved screening method by incorporating pH indicator dyes (phenol red and bromothymol blue) in ACC containing medium. This modification is based on the basic principle that ACCD action releases ammonia which can be detected by color change and zone around the bacterial colony. High color intensity and zone around the colony indicates most potent producer, colony showing only a color change indicates moderate potential and no change in colony color indicates least efficiency. Enzymatic bioassays as well as root elongation studies revealed that ACC-deaminase activity of Pseudomonas aeruginosa, Stenotrophomonas maltophilia and Bacillus subtilis clearly corresponds to their growth on dye incorporated ACC medium. This method could be used to complement the existing screening methods and to speed up the targeted isolation of agriculturally important microorganisms.