Enhancing antifungal properties of chitosan by attaching isatin-piperazine-sulfonyl-acetamide pendant groups via novel imidamide linkage.

World health organization listed fungi as priority pathogens in 2022 to counter their adverse effects on human well-being. The use of antimicrobial biopolymers is a sustainable alternative to toxic antifungal agents. In this study, we explore chitosan as an antifungal agent by grafting a novel compound N-(4-((4-((isatinyl)methyl)piperazin-1-yl)sulfonyl)phenyl) acetamide (IS). The acetimidamide linkage of IS to chitosan herein was confirmed by 13C NMR and is a new branch in chitosan pendant group chemistry. The modified chitosan films (ISCH) were studied using thermal, tensile, and spectroscopic methods. The ISCH derivatives strongly inhibit fungal pathogens of agricultural and human importance, namely Fusarium solani, Colletotrichum gloeosporioides, Myrothecium verrucaria, Penicillium oxalicum, and Candida albicans. ISCH80 showed an IC50 value of 0.85 µg/ml against M. verrucaria and ISCH100 with IC50 of 1.55 µg/ml is comparable to the commercial antifungal IC50 values of Triadiamenol (3.6 µg/ml) and Trifloxystrobin (3 µg/ml). Interestingly, the ISCH series remained non-toxic up to 2000 µg/ml against L929 mouse fibroblast cells. The ISCH series showed long-standing antifungal action, superior to our lowest observed antifungal IC50 values of plain chitosan and IS at 12.09 µg/ml and 3.14 µg/ml, respectively. ISCH films are thus suitable for fungal inhibition in an agricultural setting or food preservation.

Isolation, purification, and characterization of a novel exopolysaccharide isolated from marine bacteria Brevibacillus borstelensis M42.

Marine microbes produce polysaccharides with unique physicochemical and functional properties that help them survive in harsh marine environments. However, only a handful of marine exopolysaccharides (EPSs) have been reported to date. The present study explored the seashore of Visakhapatnam, India, to report a novel exopolysaccharide designated as Br42 produced by Brevibacillus borstelensis M42. The isolate was identified through morphological, biochemical, phylogenetic, and genome sequencing analysis. The studies on fermentation kinetics revealed that EPS Br42 was a primary metabolite with a maximum production of 1.88 ± 0.02 g/L after 60 h when production broth was fortified with 2% glucose. Additionally, EPS Br42 was found to be a heteropolysaccharide consisting of glucose and galacturonic acid with a molecular weight of about 286 kDa. Interestingly, this molecule possesses industrially relevant functional properties such as water-holding (510 ± 0.35%), oil-holding (374 ± 0.12% for coconut oil and 384 ± 0.35% for olive oil), and swelling capacities (146.6 ± 5.75%). EPS Br42 could form an emulsion that was stable at a wide pH range for about 72 h and, in fact, performed better as compared to Span 20, a commercially used synthetic emulsifier. Moreover, this EPS was also found to be heat stable and exhibited non-Newtonian pseudoplastic behavior. These physicochemical and functional properties of polysaccharides suggest that the EPS Br42 has potential for multifarious industrial applications as an emulsifier, stabilizer, viscosifier, and binding agent.

Production of Sophorolipid Biosurfactant by Insect Derived Novel Yeast Metschnikowia churdharensis f.a., sp. nov., and Its Antifungal Activity Against Plant and Human Pathogens.

Biosurfactants are potential biomolecules that have extensive utilization in cosmetics, medicines, bioremediation and processed foods. Yeast produced biosurfactants offer thermal resistance, antioxidant activity, and no risk of pathogenicity, illustrating their promising use in food formulations. The present study is aimed to assess potential of biosurfactant screened from a novel yeast and their inhibition against food spoilage fungi. A novel asexual ascomycetes yeast strain CIG-6AT producing biosurfactant, was isolated from the gut of stingless bee from Churdhar, HP, India. The phylogenetic analysis revealed that the strain CIG-6AT was closely related to Metschnikowia koreensis, showing 94.38% sequence similarity in the D1D2 region for which the name Metschnikowia churdharensis f.a., sp. nov., is proposed. The strain CIG-6AT was able to produce sophorolipid biosurfactant under optimum conditions. Sophorolipid biosurfactant from strain CIG-6AT effectively reduced the surface tension from 72.8 to 35 mN/m. Sophorolipid biosurfactant was characterized using TLC, FTIR, GC-MS and LC-MS techniques and was a mixture of both acidic and lactonic forms. Sophorolipid assessed promising activity against pathogenic fungi viz. Fusarium oxysporum (MTCC 9913), Fusarium solani (MTCC 350), and Colletotrichum gloeosporioides (MTCC 2190). The inhibitory effect of biosurfactant CIG-6AT against F. solani was studied and MIC was 49 µgm/ml, further confirmed through confocal laser scanning microscopy. We illustrated the antifungal activity of sophorolipid biosurfactant from Metschnikowia genus for the first time and suggested a novel antifungal compound against food spoilage and human fungal pathogen.

Improvisation and Evaluation of Laterosporulin Coated Titanium Surfaces for dental Applications: An In Vitro Investigation.

Despite recent improvement in implant survival rates, there remains a significant demand for enhancing the long-term clinical efficacy of titanium (Ti) implants, particularly for the prevention of peri-implantitis. Bioactive substances such as antimicrobial peptides are emerging as effective alternatives for contemporary antimicrobial agents used in dental health care. Current research work was focused to use laterosporulins that are non-haemolytic cationic antimicrobial peptides from Brevibacillus spp. for coating commercially available Ti discs. The coated Ti surfaces were evaluated in vitro for biofilm formation by two dental plaque isolates Streptococcus gordonii strain DIGK25 and S. mutans strain DIGK119 as representatives of commensal and pathogenic streptococci respectively. The biofilm inhibition was ascertained with replicated experiments on hydroxyapatite discs and confirmed by florescence microscopy. The laterosporulin coated Ti discs showed significantly reduced biofilm formation by oral streptococci and displayed promising potential to enhance the antibacterial surface properties. Such improvised Ti surfaces may curb the menace of oral streptococcal biofilm formation on dental implants and the associated implant failures.

Clostridium indicum sp. nov., a novel anaerobic bacterium isolated from the sludge of an industrial effluent.

A strictly anaerobic bacterial strain, designated as PI-S10-A1B, was isolated from a sludge sample collected from an industrial effluent dump site at Hyderabad, India. Cells stained Gram-positive and contained terminal endospores. Optimal growth was observed at 30 °C and pH 7.0. It showed negative reactions to catalase and oxidase activities. Phylogenetic analysis of the 16S rRNA gene led to strain PI-S10-A1BT being assigned to the genus Clostridium. It displayed high sequence similarity to species of cluster XIVa including Clostridium amygdalinumBR-10T (99.84 %), Clostridium saccharolyticum WM1T (98.93 %) and Clostridium indolis DSM 755T (98.31 %). It formed a coherent cluster with members of cluster XIVa. Despite high 16S rRNA gene sequence similarity, strain PI-S10-A1BT displayed only 25.3 % identity in DNA-DNA hybridization tests with C. amygdalinum BR-10T. A draft genome exhibited low values for average nucleotide identity and in silico DNA-DNA hybridization with strains of cluster XIVa. The DNA G+C content was 42.3 mol%. Major lipids were phosphatidylglycerol and diphosphatidylglycerol, with an abundance of phosphoglycolipids. Further, analysis of the draft genome revealed genomic insights against functional aspects. Considering the phenotypic differences and low genomic identity with phylogenetic relatives, strain PI-S10-A1BT is concluded to represent a new species of the genus Clostridium, for which the name Clostridiumindicum sp. nov. is proposed with type strain PI-S10-A1BT (=MTCC 12282T=DSM 24996T=JCM 32788T).