Search Results (16)

The increasing generation of agro-industrial waste and its improper disposal have raised significant environmental concerns, highlighting the urgent need for sustainable alternatives which would repurpose these materials. In this context, enzymes such as endoglucanase play a critical role in degrading lignin–cellulose biomass by catalyzing the breakdown of β-1,4-glycosidic bonds in cellulose, thereby converting it into fermentable sugars with diverse industrial applications. This study aimed to investigate the production, purification, and characterization of an endoglucanase produced by the fungus Pleurotus djamor PLO13, using coconut fiber, sugarcane bagasse, wheat bran, and pineapple crown as substrates. Endoglucanase activity was measured by the Miller method (1959), using 2% (w/v) carboxymethyl cellulose (CMC) as substrate. Solid-state fermentation (SSF) was found to be highly efficient for enzyme synthesis, with wheat bran emerging as the most effective substrate, yielding an enzyme production of 7.19 U after 120 h of cultivation. The endoglucanase was purified through ethanol precipitation and ion-exchange chromatography using DEAE-Sepharose, achieving a recovery rate of 110%, possibly due to removal of inhibitors present in the crude extract. The purified enzyme exhibited stability across a broad pH range and thermostability, with optimal activity at pH 5.0 and 50 °C. Furthermore, the enzyme was activated by EDTA, Mn²⁺, and Ca²⁺, while being inhibited by Mg²⁺. Notably, the enzyme demonstrated halotolerance, with activity increasing by 60% upon the addition of 3 M NaCl. Kinetic analysis revealed that the purified enzyme showed affinity to the CMC substrate at the analyzed parameters (pH 5.0 and 50 °C), with Km and Vmax values of 0.0997 mg/mL and 112.2 µg/min/mL, respectively. These findings suggest that the endoglucanase from P. djamor PLO13 has promising potential for biotechnological applications, underscoring the feasibility of the use of lignocellulosic waste as sustainable substrates in industrial processes. Full article

In recent years, there has been increasing interest in the study of extremophilic microorganisms, which include halophiles and halotolerants. These microorganisms, able to survive and thrive optimally in a wide range of environmental extremes, are polyextremophiles. In this context, one of the main reasons for studying them is to understand their adaptative mechanisms to stress caused by extreme living conditions. In this paper, a fungal strain Penicillium chrysogenum P13, isolated from saline soils around Pomorie Lake, Bulgaria, was used. The effect of elevated concentrations of sodium chloride on the growth and morphology as well as on the physiology of the model strain was investigated. P. chrysogenum P13 demonstrated high tolerance to NaCl, showing remarkable growth in liquid and agar media. In order to establish the relationship between salt- and oxidative stress, changes in the cell biomarkers of oxidative stress, such as oxidatively damaged proteins, lipid peroxidation, and levels of reserve carbohydrates of the studied strain were evaluated. The involvement of antioxidant enzyme defense in the adaptive strategy of the halotolerant strain against elevated NaCl concentrations was investigated. Full article

Sodin 5 is a type 1 ribosome-inactivating protein isolated from the seeds of Salsola soda L., an edible halophytic plant that is widespread in southern Europe, close to the coast. This plant, known as ‘agretti’, is under consideration as a new potential crop on saline soils. Considering a possible defence role of sodin 5 in the plant, we report here its antifungal activity against different halophilic and halotolerant fungi. Our results show that sodin 5 at a concentration of 40 µg/mL (1.4 µM) was able to inhibit the growth of the fungi Trimmatostromma salinum (35.3%), Candida parapsilosis (24.4%), Rhodotorula mucilaginosa (18.2%), Aspergillus flavus (12.2%), and Aureobasidium melanogenum (9.1%). The inhibition observed after 72 h was concentration-dependent. On the other hand, very slight growth inhibition was observed in the fungus Hortaea werneckii (4.2%), which commonly inhabits salterns. In addition, sodin 5 showed a cytotoxic effect on the Sf9 insect cell line, decreasing the survival of these cells to 63% at 1.0 µg/mL (34.5 nM). Structural analysis of sodin 5 revealed that its N-terminal amino acid residue is blocked. Using mass spectrometry, sodin 5 was identified as a homologous to type 1 polynucleotide:adenosine glycosylases, commonly known as ribosome-inactivating proteins from the Amaranthaceae family. Twenty-three percent of its primary structure was determined, including the catalytic site. Full article

Major health issues, such as the rise in oxidative stress, incidences of Alzheimer’s disease, and infections caused by antibiotic-resistant microbes, have prompted researchers to look for new therapeutics. Microbial extracts are still a good source of novel compounds for biotechnological use. The objective of the current work was to investigate marine fungal bioactive compounds with potential antibacterial, antioxidant, and acetylcholinesterase inhibitory effects. Penicillium chrysogenum strain MZ945518 was isolated from the Mediterranean Sea in Egypt. The fungus was halotolerant with a salt tolerance index of 1.3. The mycelial extract showed antifungal properties against Fusarium solani with an inhibitory percentage of 77.5 ± 0.3, followed by Rhizoctonia solani and Fusarium oxysporum with percentages of 52 ± 0.0 and 40 ± 0.5, respectively. The extract also showed antibacterial activity against both Gram-negative and Gram-positive bacterial strains using the agar diffusion technique. The fungal extract was significantly more effective with Proteus mirabilis ATCC 29906 and Micrococcus luteus ATCC 9341; inhibition zones recorded 20 and 12 mm, respectively, compared with the antibiotic gentamycin, which recorded 12 and 10 mm, respectively. The antioxidant activity of the fungus extract revealed that it successfully scavenged DPPH free radicals and recorded an IC₅₀ of 542.5 µg/mL. Additionally, it was capable of reducing Fe³⁺ to Fe²⁺ and exhibiting chelating ability in the metal ion-chelating test. The fungal extract was identified as a crucial inhibitor of acetylcholinesterase with an inhibition percentage of 63% and an IC₅₀ value of 60.87 µg/mL. Using gas chromatography–mass spectrometry (GC/MS), 20 metabolites were detected. The most prevalent ones were (Z)-18-octadec-9-enolide and 1,2-Benzenedicarboxylic acid, with ratios of 36.28 and 26.73%, respectively. An in silico study using molecular docking demonstrated interactions between the major metabolites and the target proteins, including: DNA Gyrase, glutathione S-transferase, and Acetylcholinesterase, confirming the extract’s antimicrobial and antioxidant activity. Penicillium chrysogenum MZ945518, a halotolerant strain, has promising bioactive compounds with antibacterial, antioxidant, and acetylcholinesterase inhibitory activities Full article

In order to discover a broad-specificity and high stability chitinase, a marine fungus, Aspergillus fumigatus df347, was identified in the sediments of mangrove wetlands in Qinzhou Bay, China. The chitinase gene (AfChi28) from A. fumigatus df347 was cloned and heterologously expressed in Escherichia coli, and the recombinant enzyme AfChi28 was purified and characterized. AfChi28 is an acido-halotolerant- and temperature-resistant bifunctional enzyme with both endo- and exo-cleavage functions. Its enzymatic products are mainly GlcNAc, (GlcNAc)₂, (GlcNAc)₃ and (GlcNAc)₄. Na⁺, Mg²⁺, K⁺, Ca²⁺ and Tris at a concentration of 50 mM had a strong stimulatory effect on AfChi28. The crude enzyme and pure enzyme exhibited the highest specific activity of 0.737 mU/mg and 52.414 mU/mg towards colloidal chitin. The DxDxE motif at the end of strand β5 and with Glu154 as the catalytic residue was verified by the AlphaFold2 prediction and sequence alignment of homologous proteins. Moreover, the results of molecular docking showed that molecular modeling of chitohexaose was shown to bind to AfChi28 in subsites −4 to +2 in the deep groove substrate-binding pocket. This study demonstrates that AfChi28 is a promising chitinase for the preparation of desirable chitin oligosaccharides, and provides a foundation for elucidating the catalytic mechanism of chitinases from marine fungi. Full article

Climate change has been proposed as a set of factors that affect the frequency, distribution, and morbimortality of many infectious diseases, in which mycosis has also been impacted. Most fungi have the ability to cause disease in mammalian hosts as a result of their competitive fitness advantages that allow adaptation to diverse ecological niches. Candida auris has burst in the infectious disease scenario, and it has been hypothesized that a combination of stress adaptation and biotic predation has driven this fungus in the evolution of thermotolerance and halotolerance mechanisms to adapt to different environmental niches, which have resulted in the capacity to cross the thermal infection barrier in humans. Consequently, the isolation of C. auris from estuaries in Colombia adds to the evidence that suggests that this fungus existed in the environment previously to being recognized as a human pathogen, and promotes the need for further investigations to identify additional ecological niches. Full article

Sensing and responding to changes in NaCl concentration in hypersaline environments is vital for cell survival. In this paper, we identified and characterized key components of the high-osmolarity glycerol (HOG) signal transduction pathway, which is crucial in sensing hypersaline conditions in the extremely halotolerant black yeast Hortaea werneckii and in the obligate halophilic fungus Wallemia ichthyophaga. Both organisms were isolated from solar salterns, their predominating ecological niche. The identified components included homologous proteins of both branches involved in sensing high osmolarity (SHO1 and SLN1) and the homologues of mitogen-activated protein kinase module (MAPKKK Ste11, MAPKK Pbs2, and MAPK Hog1). Functional complementation of the identified gene products in S. cerevisiae mutant strains revealed some of their functions. Structural protein analysis demonstrated important structural differences in the HOG pathway components between halotolerant/halophilic fungi isolated from solar salterns, salt-sensitive S. cerevisiae, the extremely salt-tolerant H. werneckii, and halophilic W. ichthyophaga. Known and novel gene targets of MAP kinase Hog1 were uncovered particularly in halotolerant H. werneckii. Molecular studies of many salt-responsive proteins confirm unique and novel mechanisms of adaptation to changes in salt concentration. Full article

The habitability of Mars is strongly dependent on the availability of liquid water, which is essential for life as we know it. One of the few places where liquid water might be found on Mars is in liquid perchlorate brines that could form via deliquescence. As these concentrated perchlorate salt solutions do not occur on Earth as natural environments, it is necessary to investigate in lab experiments the potential of these brines to serve as a microbial habitat. Here, we report on the sodium perchlorate (NaClO₄) tolerances for the halotolerant yeast Debaryomyces hansenii and the filamentous fungus Purpureocillium lilacinum. Microbial growth was determined visually, microscopically and via counting colony forming units (CFU). With the observed growth of D. hansenii in liquid growth medium containing 2.4 M NaClO₄, we found by far the highest microbial perchlorate tolerance reported to date, more than twice as high as the record reported prior (for the bacterium Planococcus halocryophilus). It is plausible to assume that putative Martian microbes could adapt to even higher perchlorate concentrations due to their long exposure to these environments occurring naturally on Mars, which also increases the likelihood of microbial life thriving in the Martian brines. Full article

(1) Background: Mechanisms of cellular and molecular adaptation of fungi to salinity have been commonly drawn from halotolerant strains and few studies in basidiomycete fungi. These studies have been conducted in settings where cells are subjected to stress, either hypo- or hyperosmotic, which can be a confounding factor in describing physiological mechanisms related to salinity. (2) Methods: We have studied transcriptomic changes in Aspergillus sydowii, a halophilic species, when growing in three different salinity conditions (No NaCl, 0.5 M, and 2.0 M NaCl). (3) Results: In this fungus, major physiological modifications occur under high salinity (2.0 M NaCl) and not when cultured under optimal conditions (0.5 M NaCl), suggesting that most of the mechanisms described for halophilic growth are a consequence of saline stress response and not an adaptation to saline conditions. Cell wall modifications occur exclusively at extreme salinity, with an increase in cell wall thickness and lamellar structure, which seem to involve a decrease in chitin content and an augmented content of alfa and beta-glucans. Additionally, three hydrophobin genes were differentially expressed under hypo- or hyperosmotic stress but not when the fungus grows optimally. Regarding compatible solutes, glycerol is the main compound accumulated in salt stress conditions, whereas trehalose is accumulated in the absence of salt. (4) Conclusions: Physiological responses to salinity vary greatly between optimal and high salt concentrations and are not a simple graded effect as the salt concentration increases. Our results highlight the influence of stress in reshaping the response of extremophiles to environmental challenges. Full article

One of the most commonly encountered species in the small basidiomycetous sub-phylum Wallemiomycotina is Wallemia mellicola, a xerotolerant fungus with a widespread distribution. To investigate the population characteristics of the species, whole genomes of twenty-five strains were sequenced. Apart from identification of four strains of clonal origin, the distances between the genomes failed to reflect either the isolation habitat of the strains or their geographical origin. Strains from different parts of the world appeared to represent a relatively homogenous and widespread population. The lack of concordance between individual gene phylogenies and the decay of linkage disequilibrium indicated that W. mellicola is at least occasionally recombining. Two versions of a putative mating-type locus have been found in all sequenced genomes, each present in approximately half of the strains. W. mellicola thus appears to be capable of (sexual) recombination and shows no signs of allopatric speciation or specialization to specific habitats. Full article

Salt mines are among the most extreme environments as they combine darkness, low nutrient availability, and hypersaline conditions. Based on comparative genomics and transcriptomics, we describe in this work the adaptive strategies of the true halophilic fungus Aspergillus salisburgensis, found in a salt mine in Austria, and compare this strain to the ex-type halotolerant fungal strain Aspergillus sclerotialis. On a genomic level, A. salisburgensis exhibits a reduced genome size compared to A. sclerotialis, as well as a contraction of genes involved in transport processes. The proteome of A. sclerotialis exhibits an increased proportion of alanine, glycine, and proline compared to the proteome of non-halophilic species. Transcriptome analyses of both strains growing at 5% and 20% NaCl show that A. salisburgensis regulates three-times fewer genes than A. sclerotialis in order to adapt to the higher salt concentration. In A. sclerotialis, the increased osmotic stress impacted processes related to translation, transcription, transport, and energy. In contrast, membrane-related and lignolytic proteins were significantly affected in A. salisburgensis. Full article

Twenty-eight fungal strains have been isolated from different natural marine substrates and plate screened for their production of chitinolytic activity. The two apparent best producers, Trichoderma lixii IG127 and Clonostachys rosea IG119, were screened in shaken cultures in media containing 1% colloidal chitin, 1% yeast nitrogen base and 38‰ NaCl, for their ability to produce chitinolytic enzymes under halophilic conditions. In addition, they were tested for optimal growth conditions with respect to pH, salinity and temperature. The Trichoderma strain appeared to be a slight halotolerant fungus, while C. rosea IG119 clearly showed to be a halophilic marine fungus, its optimal growth conditions being very coherent for life in the marine environment (i.e., pH 8.0, salinity 38‰). Due to its high and relatively fast activity (258 U/L after 192 h of growth) accompanied by its halophilic behaviour (growth from 0 to 160‰ of salinity), C. rosea was selected for further studies. In view of possible industrial applications, its medium for chitinolytic enzyme production was optimized by Response Surface Methodology using 1% colloidal chitin and different concentrations of corn step liquor and yeast nitrogen base (0–0.5%). Time course of growth under optimized condition showed that maximum activity (394 U/L) was recorded after 120 h on medium containing Corn Steep Liquor 0.47% and Yeast Nitrogen Base 0.37%. Maximum of productivity (3.3 U/Lh) was recorded at the same incubation time. This was the first study that demonstrated high chitinolytic activity in a marine strain of C. rosea. Full article

A global set of clinical and environmental strains of the halotolerant black yeast-like fungus Hortaea werneckii are analyzed by multilocus sequencing and AFLP, and physiological parameters are determined. Partial translation elongation factor 1-α proves to be suitable for typing because of the presence/absence of introns and also the presence of several SNPs. Local clonal expansion could be established by a combination of molecular methods, while the population from the Mediterranean Sea water also responds differently to combined temperature and salt stress. The species comprises molecular populations, which in part also differ physiologically allowing further diversification, but clinical strains did not deviate significantly from their environmental counterparts. Full article

Three new asperentin-type compounds, 6-O-α-d-ribosylasperentin (1) and 6-O-α-d-ribosyl-8-O-methylasperentin (2) and 5-hydroxyl-6-O-methylasperentin (3), along with asperentin (4) and its known analogues (5–9), were isolated from a halotolerant Aspergillus sp. strain F00785, an endotrophic fungus from marine alga. Their structures were determined using extensive NMR and HRESIMS spectroscopic analysis, including the X-ray crystallographic data for the assignment of the absolute configurations of compound 9. Compound 4 exhibited highly potent inhibitory activity against crop pathogens, Colletotrichum gleosporioides Penz. and Colletotrichum gleosporioides (Penz.) Sacc. Full article

Two new polyketides, myrothecol (1) and 5-hydroxy-3-methyl-4-(1- hydroxylethyl)-furan-2(5H)-one (2), were isolated from the fermentation broth of the halotolerant fungus Myrothecium sp. GS-17 along with three known compounds, 5-hydroxyl-3-[(1S)-1-hydroxyethyl]-4-methylfuran-2(5H)-one (3), 3,5-dimethyl-4- hydroxylmethyl-5-methoxyfuran-2(5H)-one (4), and 3,5-dimethyl-4-hydroxymethyl-5- hydroxyfuran-2(5H)-one (5). Compound 1 is the first natural occurring polyketide with a unique furylisobenzofuran skeleton. The structures of these compounds were established via extensive spectroscopic analyses including 1D-, 2D-NMR, HRESI-MS, and crystal X-ray diffraction analysis. Full article