Deciphering the potential niche of novel black yeast fungal isolates in a biological soil crust based on genomes, phenotyping, and melanin regulation

Black yeasts are polyextremotolerant fungi that contain high amounts of melanin in their cell wall and maintain a primarily yeast form. These fungi grow in xeric, nutrient deplete environments which implies that they require highly flexible metabolisms and the ability to form lichen-like mutualisms with nearby algae and bacteria. However, the exact ecological niche and interactions between these fungi and their surrounding community is not well understood. We have isolated two novel black yeast fungi of the genus Exophiala: JF 03-3F “Goopy” E. viscosium and JF 03-4F “Slimy” E. limosus, which are from dryland biological soil crusts. A combination of whole genome sequencing and various phenotyping experiments have been performed on these isolates to determine their fundamental niches within the biological soil crust consortium. Our results reveal that these Exophiala spp. are capable of utilizing a wide variety of carbon and nitrogen sources potentially from symbiotic microbes, they can withstand many abiotic stresses, and can potentially provide UV resistance to the crust community in the form of secreted melanin. Besides the identification of two novel species within the genus Exophiala, our study also provides new insight into the production and regulation of melanin in extremotolerant fungi.

Role of Actinomycete sp. in Bio-extraction of Copper from Electronic Waste

Copper is bioleached from printed circuit boards (PCBs) using Actinomycete sp. It was identified by 16S rRNA, called Streptomyces graminofaciens. The tolerance of S. graminofaciens towards copper showed that it couldn’t live in the presence of copper sulfate. The process was carried out by culturing 3.09×103 CFU of S. graminofaciens in 50 ml of modified starch nitrate medium for three days at 200 rpm and 30C and then 0.5% e-waste was added for other 5 days. Glucose (0.01 g/ml) and ammonium sulfate (0.002g/ml) were the best carbon and nitrogen sources. At pH 5, the leached copper was 88.1%. The bio-dissolution mechanism was investigated via the production of enzymes of S. graminofaciens metabolites, which showed that the higher dissolution has occurred in an un-denatured sample (non-heating) than the denatured one (heating). FTIR spectra confirmed the action of S. graminofaciens through the disappearance and appearance of some peaks. SEM showed that the e-waste gained more pores as a result of bio-treatment, which refers to the liberation of metals in solution.

The role of carbon and nitrogen sources in the production of bioactive compounds in Monascus fermentation products: a mini review

Angkak is one of the Monascus fermented products with rice as a substrate. In addition, Chinese yam, potatoes, soybean, ginseng and onions can be used as a substrate for fermentation products by Monascus sp. It was known that the fermented product by Monascus sp. produces several bioactive compounds that have antihyperlipidemic activity. These bioactive compounds are monacolin-K and pigment compounds (monascin and ankaflavin). Each of these compounds has different cholesterol inhibitory activity. The production of these bioactive compounds is strongly influenced by the nutritional composition of the fermentation media. The addition of the right carbon and nitrogen sources can accelerate the production of bioactive compounds by Monascus sp.

Production of Phytase by three thermophilic fungi

Production of phytase by three thermophilic fungi, Thermomyces lanuginosus, Talaromyces luteus and Rhizomucor pusillus under different cultural conditions was assessed. Temperature of 45°C, pH-6.0 were optimum for phytase production by the all three fungi under investigation . Carbon and nitrogen sources for production of phytases by the three thermophilic fungi varied with the fungus. When T. lanuginosus opted for D-glucose followed by D-fructose, T. luteus preferred D-glucose, D-mannose and mannitol for production a phytase. On the other hand, R. pusillus produced maximum phytase during its growth on mannitol and maltose as carbon source. L- asparagine, L- arginine and L-asparatic acid were preferred nitrogen sources for production of phytase by T. lanuginosus. On the other hand T. luteus, opted for L- asparagine, L-glutamic acid and L- glycine for the activity of phytase. R. pusillus produced maximum phytase in medium containing L-argine, L-asparagine and L- asparatic acid.

Epiphytic Bacteria from Sweet Pepper Antagonistic In Vitro to Ralstonia solanacearum BD 261, a Causative Agent of Bacterial Wilt

Biological control of plant pathogens, particularly using microbial antagonists, is posited as the most effective, environmentally-safe, and sustainable strategy to manage plant diseases. However, the roles of antagonists in controlling bacterial wilt, a disease caused by the most devastating and widely distributed pathogen of sweet peppers (i.e., R. solanacearum), are poorly understood. Here, amplicon sequencing and several microbial function assays were used to depict the identities and the potential antagonistic functions of bacteria isolated from 80 red and green sweet pepper fruit samples, grown under hydroponic and open soil conditions, with some plants, fungicide-treated while others were untreated. Amplicon sequencing revealed the following bacterial strains: Bacillus cereus strain HRT7.7, Enterobacter hormaechei strain SRU4.4, Paenibacillus polymyxa strain SRT9.1, and Serratia marcescens strain SGT5.3, as potential antagonists of R. solanacearum. Optimization studies with different carbon and nitrogen sources revealed that maximum inhibition of the pathogen was produced at 3% (w/v) starch and 2,5% (w/v) tryptone at pH 7 and 30 °C. The mode of action exhibited by the antagonistic isolates includes the production of lytic enzymes (i.e., cellulase and protease enzymes) and siderophores, as well as solubilization of phosphate. Overall, the results demonstrated that the maximum antimicrobial activity of bacterial antagonists could only be achieved under specific environmental conditions (e.g., available carbon and nitrogen sources, pH, and temperature levels), and that bacterial antagonists can also indirectly promote crop growth and development through nutrient cycling and siderophore production.

Isolation and Selection of Purple Non-Sulfur Bacteria for Nutrient Rich Biomass Production from Wastes

Purple nonsulfur bacteria (PNSB) are anoxygenic photosynthetic bacteria, which are able to photoheterotrophically grow in the presence of excessive nutrients. Hence, PNSB can convert organic components, in waste waters into nutrient rich biomass. This suggests the feasibility of converting wastes into valuable products. In this research, method for isolation of PNSB was optimized, and subsequently used for the isolation of PNSB from domestic waste and pond water samples taken in Hanoi. In addition, the effects of carbon and nitrogen sources and types of waste on biomass and nutrients (protein and carotenes) were also investigated. Four PNSB strains were isolated and based on comparative 16S rDNA analysis and their morphological characteristics, they were identified as Rhodobacter (Rb.) capsulatus, Rhodobacter (Rb.) sphaeroides, Rhodobacter (Rb.) sediminis and Rhodopseudomonas (Rp.) palustris. In terms of the effects of carbon and nitrogen sources on their biomass and nutrient production, glucose or maltose and ammonium chloride or urea were found to be more enhancive than starch and peptone, respectively. Among the studied strains, Rb. capsulatus MD1 and Rb. sphaeroides MD3 showed significantly higher biomass production (up to 0.7 g/l) when growing with various carbon and nitrogen sources, in comparison with the other strains. Moreover, MD1 and MD3 also produced at least four-fold more carotenoid and up to two-fold more protein in tofu processing wastewater compared with the other wastewater. The results suggest potential applications of the PNSB strains for efficient conversions of organic compounds in wastes into biomass of high nutritional values.