No abstract

Natural melanin with many interesting properties has potential applications in cosmetics, drug delivery, semiconductors, etc. However, conventional production methods are not efficient, resulting in its high cost (350−650 USD g −1 ), which has been a bottleneck for its efficient commercial utilization. To explore a faster extraction method with a higher yield, a melanin-producing endophytic bacterium was isolated from the halophyte Salicornia brachiata and further identified as Bacillus subtilis 4NP-BL by phylogenetic analysis of 16S rRNA gene sequences. The maximum melanin yield of up to 1.5 g dry wt L −1 of production media was obtained through central composite design (CCD). The isolated melanin belonged to the eumelanin class with an irregular structure on the basis of elemental analysis, UV−vis, Fourier transform infrared (FT-IR), scanning electron microscopy (SEM), electron paramagnetic resonance (EPR), and NMR studies. Furthermore, purified melanin displayed antioxidant activity and antimicrobial activity against pathogens Xanthomonas campestris and Alteromonas macleodii. Thus, this study further suggests a probable role of endophytes that produce melanin in aiding host plant protection from environmental stress and other pathogens.

Untapped natural habitats like halophytes, marsh land, and marine environment are suitable arena for chemical ecology between plants and microbes having environmental impact. Endophytes constitute an ecofriendly option for the promotion of plant growth and to serve as sustainable resources of novel bioactive natural products. The present study focusing on biodiversity of bacterial endophytes from Salicornia brachiata, led to isolation of around 350 bacterial endophytes. Phylogenetic analysis of 63 endophytes revealed 13 genera with 29 different species, belonging to 3 major groups: Firmicutes, Proteobacteria and Actinobacteria. 30% isolates belonging to various genera demonstrated broadspectrum antibacterial and antifungal activities against a panel of human, plant, and aquatic infectious agents. An endophytic isolate Bacillus amyloliquefaciens 5NPA-1, exhibited strong in-vitro antibacterial activity against human pathogen S. aureus and phytopathogen X. campestris. Investigation through LC-MS/MS-based molecular networking and bioactivity-guided purification led to the identification of three bioactive compounds belonging to lipopeptide class on the basis of 1 H-and 13 C-NMR and MS analysis. To our knowledge, this is the first report studying bacterial endophytic biodiversity of Salicornia brachiata and isolation of bioactive compounds from its endophyte. Overall, the present study provides insights into the diversity of endophytes associated with the plants from the extreme environment as rich source of metabolites with remarkable agricultural applications and therapeutic properties.

Natural melanin biopolymers have multifarious activities, but their commercial exploitation is obstructed due to their high price, unsustainable source, use of harmful solvents, and low extraction yield. Conventional techniques for the extraction of the melanin biopolymer encounter several disadvantages such as poor extraction efficiency, excessive use of acid and alkali, and lengthy time duration. Due to the heterogeneous and complex structure of melanin, it is insoluble in most of the organic solvents as well as water and is less soluble in DMSO and alkaline pH. Herein, the suitability of an aqueous solution of quaternary ammonium hydroxide known as tetrabutylammonium hydroxide (40% w/w TBAOH in water) to extract the melanin biopolymer from the endophyte Streptomyces hyderabadensis 7VPT5-5R was investigated. The aqueous TBAOH extraction method led to a 66% increase in the yield of melanin in comparison to the conventional method of extraction. The used solvent was further recycled for five consecutive cycles with melanin yields ranging from 5.54 ± 0.03 to 5.47 ± 0.02 g/L. Considering the efficiency of the aqueous TBAOH for effective extraction of melanin and its recyclability potential, it can be considered as a sustainable solvent for the large-scale extraction of pigments from bacterial culture.

Melanins are natural biopolymers that are non-toxic, have a wide range of distribution in different biosystems, and play significant physiological roles. Eumelanin is an indolic biopolymer with catechol and heteroatom...

Melanins have multidimensional applications in medical and biomaterial science and thereby shooting up its demand. Conventional extraction techniques has many disadvantages like poor extraction efficiency, use of toxic solvents (acid and base), time-consuming, and consequent higher cost of the final product. To tackle this problem, an innovative ionic liquid (IL) based approach was used for the extraction and purification of melanin from the endophyte Streptomyces hyderabadensis strain 7VPT5-5R. ILs are furnished with best thermal, chemical, electrochemical stability, non flammability, trivial volatility, and broad range of solubility making them a promising medium for the extraction of melanin. Maximum yield 5.5 g/L was obtained by IL extraction method which is remarkably higher than conventional acid-precipitation method. The devised method also allows recyling of IL five times without loosing efficinecy, thus reducing use of fresh IL. Furthermore, the process is scalable, eco-friendly, rapid and produce superior quality melanin than that of the conventional method.

Untapped natural habitats like halophytes, marsh land, and marine environment are suitable arena for chemical ecology between plants and microbes having environmental impact. Endophytes constitute an ecofriendly option for the promotion of plant growth and to serve as sustainable resources of novel bioactive natural products. The present study focusing on biodiversity of bacterial endophytes from Salicornia brachiata, led to isolation of around 350 bacterial endophytes. Phylogenetic analysis of 63 endophytes revealed 13 genera with 29 different species, belonging to 3 major groups: Firmicutes, Proteobacteria and Actinobacteria. 30% isolates belonging to various genera demonstrated broad-spectrum antibacterial and antifungal activities against a panel of human, plant, and aquatic infectious agents. An endophytic isolate Bacillus amyloliquefaciens 5NPA-1, exhibited strong in-vitro antibacterial activity against human pathogen S. aureus and phytopathogen X. campestris. Investigation through LC-MS/MS-based molecular networking and bioactivity-guided purification led to the identification of three bioactive compounds belonging to lipopeptide class on the basis of 1H- and 13C-NMR and MS analysis. To our knowledge, this is the first report studying bacterial endophytic biodiversity of Salicornia brachiata and isolation of bioactive compounds from its endophyte. Overall, the present study provides insights into the diversity of endophytes associated with the plants from the extreme environment as rich source of metabolites with remarkable agricultural applications and therapeutic properties.

The present study explores the endophyte associated with the halophyte Salicornia brachiata for uncovering new biologically important compounds. Thus, HPLC‐PDA guided chemical investigation of the ethyl acetate extract of the Bacillus subtilis NPROOT3 led to the isolation of a new compound named bacillinaphthin A (1) along with previously known rubinaphthin A (2). The structure of 2 was determined by a comparison of HR‐ESI‐MS, 1H and 13C nuclear magnetic resonances (NMR) with those of reported data, whereas the structure of new compound 1 was elucidated by interpretation of 1D‐ and 2D‐NMR and MS data. Bacillinaphthin (1) and rubinaphthin (2) feature 1,4‐dihydroxy‐2‐naphthoic acid derivatives which have been isolated herein for the first time from the genus Bacillus. Bacillinaphthin (1) is a new congener of 2 with an additional succinic acid side chain attached to the sugar moiety. Production of succinoglycan compounds was reported to regulate symbiosis, hence the isolation of 1 exhibits an example of chemical ecology between the halophyte and its endophyte. In silico tools were used to assess the bioactive potential of both isolated molecules.