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.
Seaweeds are macroscopic forms of phylogenetically diverse assemblage of marine algae that grow in oceans, thriving among profoundly harsh environmental conditions. They are cultivated in many maritime nations primarily for edible applications; besides hydrocolloid extraction is the second largest domain of utility for this renewable biomass. The farming practices have been traditionally evolved in different Southeast Asian countries. Nevertheless, advancement in the knowledge about their life‐history traits and control over reproduction has paved ways for commencement of large‐scale commercial farming. Food and Agriculture Organisation of United Nations reported the availability of 35.8 million tons of seaweed biomass globally of which 97% accounted for farming. Although cultivation is on the rise due to relevant to social gains, epiphytic infestation, diseases and grazing have been identified as leading causes that result in substantially lower yield, deteriorated quality of product and skewed economics. Epiphytes may considerably impact the interaction of seaweed hosts with other beneficial communities also. Epidemiological studies in natural seaweed populations are scarce and this makes the understanding of the cross‐talk involving host specificity, and their role obscure. An overview of the diversity of epiphytes, understanding of mechanism of action, factors responsible, chemistry behind their interaction will help in deciphering the solutions to overcome infestation. A comprehensive report of seaweed epiphytism, diseases and grazing from the aspects of host–epiphyte interaction and their resultant consequences is presented along with the studies on economic impacts. The role of multi‐omics approaches in delineating seaweed epiphytic interactions is also included.
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 bacterial flora associated with Gracilaria dura, the sole producer of natural agarose was obtained. Screening for the presence of various enzymes and bioactive compounds resulted in discerning different clinically and industrially important enzymes. Three isolates were identified to be producing L-asparaginase (LA), a potent anticancer drug. The strain 4T1-C26E registered highest LA activity (25.2 IU ml− 1) in the enzyme assay, was selected for yield improvement by optimizing process parameters through Response Surface Methodology (RSM). Various parameters like glucose concentration, L-asparagine concentration, pH of the media, and incubation period were optimized through Central Composite Design (CCD) for enhanced yield of LA by 4T1-C26E, identified as Bacillus licheniformis. The CCD table was exploited for application in artificial neural networking (ANN) for the development of optimum method of cultivation. In this study, we obtained 2.5-fold (88.4 IU ml− 1) increase in LA production by this strain through RSM optimization. Further, Artificial Neural Networking Particle Swarm Optimization (ANN-PSO) predicted the input combinations. The experimental validation of LA production was found to be 4-fold (126.4 IU ml− 1) higher with respect to the unoptimized conditions. This illustrates the effectiveness of ANN-PSO based optimization technique, the error percent between the predicted and experimental output was 4.03%. The most important benefit of LA from 4T1-C26E is that it possesses no L-glutaminase activity. Further, it is extracellularly produced which is suitable for easier downstream processing thereby reducing chances of immunogenic responses by endotoxins. However, characterization of kinetic parameters and cytotoxic studies on cell cultures are mandatory to confirm its pharmaceutical application.
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