Endophytic Fungi-Mediated Biocatalysis and Biotransformations Paving the Way Toward Green Chemistry

Isolation of native microorganisms from Shengli lignite and study on their ability to dissolve lignite

To more greenly and efficiently utilize the abundant lignite resources and explore the microbial degradation and transformation potential of lignite for its environmentally friendly and resourceful utilization, Shengli lignite from the Hulunbuir region of Inner Mongolia, China, was selected as the research subject. Through the dilution plating method and streaking method, 31 native microorganisms were successfully isolated from the Shengli lignite, including 16 bacteria and 15 fungi. After microbial coal dissolution experiments, it was found that certain microorganisms have a significant dissolving effect on lignite, with some bacterial and fungal strains showing strong dissolution capabilities. In particular, the bacterium SH10 Lysinibacillus fusiformis and the fungus L1W Paecilomyces lilacinus demonstrated the best coal-dissolving abilities, with dissolution rates both reaching 60%. The products of microbial dissolution of lignite were analyzed using gas chromatography-mass spectrometry (GC-MS) technology, identifying a variety of small molecular organic compounds, including alkanes, alcohols, esters, and phenols. The results of this study provide a new perspective on the biodegradation of lignite and lay the foundation for the development of new lignite treatment and utilization technologies.

Adsorptive performances and valorization of green synthesized biochar-based activated carbon from banana peel and corn cob composites for the abatement of Cr(VI) from synthetic solutions: Parameters, isotherms, and remediation studies

This study intended to remove Cr(VI) from an aqueous synthetic solution employing synthesized biochar adsorbent from a blend of locally sourced banana peel, and corn cob biomass wastes. An equal ratio of the prepared powder was activated with ZnCl2 solution (1:1 wt basis) and carbonized for 2 h at 600 °C. The proximate analysis of the selected BP-CCAC@ZC3 biochar was conducted. Subsequently, its surface area, surface functions, and morphology were examined using BET analysis, FTIR, and SEM techniques, respectively. The proximate analysis of BP-CCAC@ZC3 showed a moisture content of 2.37 ± 0.80 %, an ash content of 8.07 ± 0.75 %, volatile matter of 19.38 ± 2.66 %, and fixed carbon of 70.18 %. It was found that the synthesized BP-CCAC@ZC3 had 432.149 m2/g of a specific area as per the BET surface area analysis. The highest efficiency for Cr(VI) removal was determined to be 97.92 % through adsorption batch tests using a dose of 0.4 g of BP-CCAC@ZC3, an initial Cr(VI) concentration of 20 mg/L, pH of 2, and 35 min contact time. Likewise, the adsorption process was effectively described by the Langmuir isotherm model, which had a high correlation coefficient (R 2 = 0.9977) and a maximum adsorption capacity of 19.16 mg/g, indicating a monolayer adsorption mechanism. The BP-CCAC@ZC3 biochar exhibited reusability for up to four cycles with only a slight decrease in effectiveness, highlighting its potential for sustainable wastewater treatment. Overall, using corn cob and banana peel composites to synthesize activated carbon with ZnCl2 offers a promising method for effectively removing Cr(VI) containing wastewater.

Progress on metabolites of Astragalus medicinal plants and a new factor affecting their formation: Biotransformation of endophytic fungi

It is generally believed that the main influencing factors of plant metabolism are genetic and environmental factors. However, the transformation and catalysis of metabolic intermediates by endophytic fungi have become a new factor and resource attracting attention in recent years. There are over 2000 precious plant species in the Astragalus genus. In the past decade, at least 303 high-value metabolites have been isolated from the Astragalus medicinal plants, including 124 saponins, 150 flavonoids, two alkaloids, six sterols, and over 20 other types of compounds. These medicinal plants contain abundant endophytic fungi with unique functions, and nearly 600 endophytic fungi with known identity have been detected, but only about 35 strains belonging to 13 genera have been isolated. Among them, at least four strains affiliated to Penicillium roseopurpureum, Alternaria eureka, Neosartorya hiratsukae, and Camarosporium laburnicola have demonstrated the ability to biotransform four saponin compounds from the Astragalus genus, resulting in the production of 66 new compounds, which have significantly enhanced our understanding of the formation of metabolites in plants of the Astragalus genus. They provide a scientific basis for improving the cultivation quality of Astragalus plants through the modification of dominant fungal endophytes or reshaping the endophytic fungal community. Additionally, they open up new avenues for the discovery of specialized, green, efficient, and sustainable biotransformation pathways for complex pharmaceutical intermediates.

Plant endophytic fungi exhibit diverse biotransformation pathways of mogrosides and show great potential application in siamenoside I production

Fungal endophytes, as an untapped resource of glycoside hydrolase biocatalysts, need to be further developed. Mogroside V, the primary active compound in Siraitia grosvenorii fruit, can be converted into other various bioactive mogrosides by selective hydrolysis of glucose residues at C3 and C24 positions. In present study, 20 fungal strains were randomly selected from our endophytic fungal strain library to assess their capability for mogroside V transformation. The results revealed that relatively high rate (30%) endophytic fungal strains exhibited transformative potential. Further analysis indicated that endophytic fungi could produce abundant mogrosides, and the pathways for biotransforming mogroside V showed diverse. Among the given fungal endophytes, Aspergillus sp. S125 almost completely converted mogroside V into the end-products mogroside II A and aglycone within just 2 days of fermentation; Muyocopron sp. A5 produced rich intermediate products, including siamenoside I, and the end-product mogroside II E. Subsequently, we optimized the fermentation conditions for Aspergillus sp. S125 and Muyocopron sp. A5 to evaluate the feasibility of large-scale mogroside V conversion. After optimization, Aspergillus sp. S125 converted 10 g/L of mogroside V into 4.5 g/L of mogroside II A and 3.6 g/L of aglycone after 3 days of fermentation, whereas Muyocopron sp. A5 selectively produced 4.88 g/L of siamenoside I from 7.5 g/L of mogroside V after 36 h of fermentation. This study not only identifies highly effective biocatalytic candidates for mogrosides transformation, but also strongly suggests the potential of plant endophytic fungi as valuable resources for the biocatalysis of natural compounds.

Cultivable Endophyte Resources in Medicinal Plants and Effects on Hosts

With the increasing demand for medicinal plants and the increasing shortage of resources, improving the quality and yield of medicinal plants and making more effective use of medicinal plants has become an urgent problem to be solved. During the growth of medicinal plants, various adversities can lead to nutrient loss and yield decline. Using traditional chemical pesticides to control the stress resistance of plants will cause serious pollution to the environment and even endanger human health. Therefore, it is necessary to find suitable pesticide substitutes from natural ingredients. As an important part of the microecology of medicinal plants, endophytes can promote the growth of medicinal plants, improve the stress tolerance of hosts, and promote the accumulation of active components of hosts. Endophytes have a more positive and direct impact on the host and can metabolize rich medicinal ingredients, so researchers pay attention to them. This paper reviews the research in the past five years, aiming to provide ideas for improving the quality of medicinal plants, developing more microbial resources, exploring more medicinal natural products, and providing help for the development of research on medicinal plants and endophytes.

A review on the immobilization of pepsin: A Lys-poor enzyme that is unstable at alkaline pH values

Pepsin is a protease used in many different applications, and in many instances, it is utilized in an immobilized form to prevent contamination of the reaction product. This enzyme has two peculiarities that make its immobilization complex. The first one is related to the poor presence of primary amino groups on its surface (just one Lys and the terminal amino group). The second one is its poor stability at alkaline pH values. Both features make the immobilization of this enzyme to be considered a complicated goal, as most of the immobilization protocols utilize primary amino groups for immobilization. This review presents some of the attempts to get immobilized pepsin biocatalyst and their applications. The high density of anionic groups (Asp and Glu) make the anion exchange of the enzyme simpler, but this makes many of the strategies utilized to immobilize the enzyme (e.g., amino-glutaraldehyde supports) more related to a mixed ion exchange/hydrophobic adsorption than to real covalent immobilization. Finally, we propose some possibilities that can permit not only the covalent immobilization of this enzyme, but also their stabilization via multipoint covalent attachment.

Endophytic fungi: a potential source of industrial enzyme producers

Microbial enzymes have gained interest for their widespread use in various industries and medicine due to their stability, ease of production, and optimization. Endophytic fungi in plant tissues produce a wide range of secondary metabolites and enzymes, which exhibit a variety of biological activities. The present review illustrates promising applications of enzymes produced by endophytic fungi and discusses the characteristic features of the enzymes, application of the endophytic fungal enzymes in therapeutics, agriculture, food, and biofuel industries. Endophytic fungi producing ligninolytic enzymes have possible biotechnological applications in lignocellulosic biorefineries. The global market of industrially important enzymes, challenges, and future prospects are illustrated. However, the commercialization of endophytic fungal enzymes for industrial purposes is yet to be explored. The present review suggests that endophytic fungi can produce various enzymes and may become a novel source for upscaling the production of enzymes of industrial use.

Endophytic fungi from Dongxiang wild rice (Oryza rufipogon Griff.) show diverse catalytic potential for converting glycyrrhizin

Endophytic fungi inhabiting niche environments are novel biocatalyst resources that need to be exploited urgently. In this study, 63 endophytic fungi isolated from Dongxiang wild rice (Oryza rufipogon Griff.) were tested to assess their potentials to transform glycyrrhizin (GL) into glycyrrhetinic acid monoglucuronide (GAMG) or glycyrrhetinic acid (GA), of which 12 strains were shown to have β-d-glucuronidase activity. Based on morphological characteristics and rDNA ITS sequence analysis, the strains S59, L138, L55 and R57 with high GL molar conversion rates (55%, 45%, 65% and 89%) were further identified as Microsphaeropsis arundinis S59, Penicillium rubens L138, Aspergillus flavus L55 and Eupenicillium javanicum R57, respectively. These four strains with four different types of GL conversion processes were identified, i.e., (1) GL → GAMG in M. arundinis S59, (2) GL → GAMG and GA in A. flavus L55, (3) GL → GA in P. rubens L138, and (4) GL → GAMG → GA in E. javanicum R57, in which the bioconversion type (4) is reported for the first time. The study not only provided abundant and diverse β-d-glucuronidase resources that can be used for GL bioconversion, especially for GAMG biosynthesis from endophytic fungi, but also expanded our knowledge of potential roles of endophytes as new biocatalysts in biotransformation.