Fungal degradation of lantadene A, the pentacyclic triterpenoid hepatotoxin of lantana plant

Seven white-rot fungi, known to degrade complex biomolecules and xenobiotics were used for investigation on biodegradation of lantadene A (LA), the bioactive pentacyclic triterpenoid of Lantana camara. Pleurotus sajor-caju and Merulius tremellosus PRL-2845 did not degrade LA. Trametes versicolor MTCC-138, Heterobasidion annosum MTCC-146, Phellinus pini RAB-83-19, Pleurotus ostreatus MTCC-142 and Phlebia radiata 2 utilized LA to the extent of 11–15.7%. This is the first report on the fungal degradation of a pentacyclic triterpenoid.     

Fungal degradation of carbohydrate-linked polystyrenes

A series of carbohydrate molecules like glucose, sucrose and lactose were linked to maleic anhydride functionalized polystyrene by polymer analogous reactions to produce biodegradable polymers. Pure culture system was used for evaluating the biodegradability of these sugar linked polystyrene-maleic anhydride copolymers by known fungal test organisms. Weight loss measurements after fungal treatment confirmed the biodegradability of the carbohydrate-linked polymers, and it was observed that the degree of susceptibility to degradation varied with the type of test organism as well as with the type of sugar. FTIR spectra confirmed the degradation of the polymer.     

How the walls come crumbling down: recent structural biochemistry of plant polysaccharide degradation

The recent years have witnessed considerable developments in the interpretation of the three-dimensional structures of plant polysaccharide-degrading enzymes in the context of their functional specificity. A plethora of new structures of catalytic, carbohydrate-binding and protein-scaffolding modules involved in (hemi)cellulose catabolism has emerged in harness with sophisticated biochemical analysis. Despite significant advances, a full understanding of the intricacies of substrate recognition and catalysis by these diverse and specialised enzymes remains an important goal, especially if the application potential of these biocatalysts is to be fully realised.     

The iota-carrageenase of Alteromonas fortis. A beta-helix fold-containing enzyme for the degradation of a highly polyanionic polysaccharide

Carrageenans are gel-forming hydrocolloids extracted from the cell walls of marine red algae. They consist of d-galactose residues bound by alternate alpha(1-->3) and beta(1-->4) linkages and substituted by one (kappa-carrageenan), two (iota-carrageenan), or three (lambda-carrageenan) sulfate-ester groups per disaccharide repeating unit. Both the kappa- and iota-carrageenan chains adopt ordered conformations leading to the formation of highly ordered aggregates of double-stranded helices. Several kappa-carrageenases and iota-carrageenases have been cloned from marine bacteria. Kappa-carrageenases belong to family 16 of the glycoside hydrolases, which essentially encompasses polysaccharidases specialized in the hydrolysis of the neutral polysaccharides such as agarose, laminarin, lichenan, and xyloglucan. In contrast, iota-carrageenases constitute a novel glycoside hydrolase structural family. We report here the crystal structure of Alteromonas fortis iota-carrageenase at 1.6 A resolution. The enzyme folds into a right-handed parallel beta-helix of 10 complete turns with two additional C-terminal domains. Glu(245), Asp(247), or Glu(310), in the cleft of the enzyme, are proposed as candidate catalytic residues. The protein contains one sodium and one chloride binding site and three calcium binding sites shown to be involved in stabilizing the enzyme structure.     

Fungal degradation of anaerobically digested sewage sludge

Fifty isolates of fungi were screened for their ability to grow on and degrade sludge. Cunninghamella elegans was selected for further study of degradation as affected by moisture, nutrients, time and temperature. Maximal sludge degradation (total dry weight basis) was 5.8% by Rhizopus oligosporus, 5.4% by C. elegans and 5.3% by Myrothecium verrucaria, representing approximately 11% degradation of the organic matter present. Added nutrients had little or no effect on sludge degradation. Maximal sludge degradation by C. elegans occurred in three weeks at 30–35 C or four weeks at 25 and 40 C.Sewage sludge is a stable humic material that breaks down slowly with time when mixed with soil. The disposal of sewage sludge is one of the problems of environmental pollution throughout the world. Approximately 455,000 cubic meters of sewage sludge are produced daily in the United States (7). The development of supplementary methods of sewage treatment to be used in tandem with anaerobic digestors are of current interest. Benefits of such a tandem system utilizing fungi would be the acceleration of recycling of waste, supplemental detoxification of sludge, and perhaps even recovery of utilizable protein. The use of fungi to accelerate sludge degradation with the possible side benefits of production of protein or other recoverable metabolites has not been investigated. This paper reports the screening of fifty fungi for their ability to grow on and degrade anaerobically digested sewage sludge and the determination of the level of protein produced by C. elegans on this medium.Portions of this investigation were submitted to Auburn University by W.M.H. in partial fulfillment of the requirements of the M.S. degree.Research and Technology of the U.S. Department of the Interior through the Water Resources Research Institute of Auburn University Project A-030-Ala.     

Fungal degradation of polyhydroxyalkanoates and a semiquantitative assay for screening their degradation by terrestrial fungi.

The current problems with decreasing fossile resources and increasing environmental pollution by petrochemical-based plastics have stimulated investigations to find biosynthetic materials which are also biodegradable. Bacterial reserve materials such as polyhydroxyalkanoates (PHA) have been discovered to possess thermoplastic properties and can be synthesized from renewable resources. Poly-beta-hydroxybutyric acid (PHB) is at present the most promising PHA; and BIOPOL, its copolymer with poly-beta-hydroxy-valerate (PHV), is already industrially produced (ICI, UK), and used as packaging material (WELLA, FRG). According to the literature, PHA degradation has so far mainly been observed in bacteria; only under certain environmental conditions has fungal degradation of PHAs been indicated. Since fungi constitute an important part of microbial populations participating in degradation processes, a simple screening method for fungal degradation of BIOPOL, a PHA-based plastic, was developed. Several media with about 150 fungal strains from different terrestrial environments and belonging to different systematic and ecological groups were used. PHA depolymerization was tested on three PHB-based media, each with 0.1% BIOPOL or PHB homopolymer causing turbidity of the medium. The media contained either a comparatively low or high content of organic carbon (beside PHA) or were based on mineral medium with PHA as the principal source of carbon. The degradation activity was detectable due to formation of a clear halo around the colony (Petri plates) or a clear zone under the colony (test tubes).(ABSTRACT TRUNCATED AT 250 WORDS)     

Recalcitrant polysaccharide degradation by novel oxidative biocatalysts

The classical hydrolytic mechanism for the degradation of plant polysaccharides by saprophytic microorganisms has been reconsidered after the recent landmark discovery of a new class of oxidases termed lytic polysaccharide monooxygenases (LPMOs). LPMOs are of increased biotechnological interest due to their implication in lignocellulosic biomass decomposition for the production of biofuels and high-value chemicals. They act on recalcitrant polysaccharides by a combination of hydrolytic and oxidative function, generating oxidized and non-oxidized chain ends. They are copper-dependent and require molecular oxygen and an external electron donor for their proper function. In this review, we present the recent findings concerning the mechanism of action of these oxidative enzymes and identify issues and questions to be addressed in the future.     

Fungal degradation of pine and straw alkali lignins

Summary Kraft pine and straw lignins were fractionated into aqueous soluble and organic soluble-ether insoluble parts. Chemical analysis, UV characteristics, and gel permeation chromatograms of crude and fractionated lignins were studied. Using pure and mixed, N-limited and non N-limited standing cultures of several fungal species, the biodegradability of curde and fractionated lignins was compared. Straw lignins, especially the aqueous fraction were degraded by most of the fungi studied. Except for Sporotrichum pulverulentum, nitrogen limitation did not seem to favour degradation. The best fungi for degradation under conditions of N-limitation were S. pulverulentum, Humicola fuscoatra, and Aspergillus wentii, under sufficient nitrogen: A. wentii, Chaetomium cellulolyticum and H. fuscoatra. The greatest percentage degradation, 55%, was obtained with S. pulverulentum under nitrogen limited conditions from 1 gl^–1 organic soluble-ether insoluble kraft lignin. Gel chromatography showed that the degradation was over the complete molecular size range.     

Fungal degradation of benzoic acid and related compounds

Most knowledge of the degradation of aromatic compounds has been gained through investigation of the pathways in bacteria. In recent years, however, significant developments have been made in the understanding of the degradation of these compounds in yeasts and moulds. Many similarities have been identified between the bacteria and the yeasts and moulds but some significant differences occur. This review highlights these differences and discusses the current understanding of the fungal degradation of benzoate and some substituted benzoates. The pathways for the further conversion of the ring-fission substrates, which are common to all fungi capable of degrading these aromatic compounds, are also presented.J.D. Wright was with the Department of Applied Biology, University of Hull, Hull HU6 7RX, UK and is now with Castrol International, Castrol Technology Centre, Whitchurch Hill, Pangbourne, Reading RG8 7QR, UK.     

Developments and opportunities in fungal strain engineering for the production of novel enzymes and enzyme cocktails for plant biomass degradation

Fungal strain engineering is commonly used in many areas of biotechnology, including the production of plant biomass degrading enzymes. Its aim varies from the production of specific enzymes to overall increased enzyme production levels and modification of the composition of the enzyme set that is produced by the fungus. Strain engineering involves a diverse range of methodologies, including classical mutagenesis, genetic engineering and genome editing. In this review, the main approaches for strain engineering of filamentous fungi in the field of plant biomass degradation will be discussed, including recent and not yet implemented methods, such as CRISPR/Cas9 genome editing and adaptive evolution.     

Fungal pectic enzyme fractionation by dye affinity chromatography

Summary A dye affinity fractionation of a commercial pectic enzyme preparation is described. From nine immobilized triazinic dyes assayed, only Blue R-HE and Yellow 4R-HE were able to retain pectin lyase thus allowing the obtention of a fraction not producing methanol during fruit juice clarification. While pectinesterase did not bind to the Chromatographic matrix, the retained pectin lyase could be quantitatively eluted with a salt gradient.     

Mapping the polysaccharide degradation potential of Aspergillus niger

ABSTRACT: BACKGROUND: The degradation of plant materials by enzymes is an industry of increasing importance. For sustainable production of second generation biofuels and other products of industrial biotechnology, efficient degradation of non-edible plant polysaccharides such as hemicellulose is required. For each type of hemicellulose, a complex mixture of enzymes is required for complete conversion to fermentable monosaccharides. In plant-biomass degrading fungi, these enzymes are regulated and released by complex regulatory structures. In this study, we present a methodology for evaluating the potential of a given fungus for polysaccharide degradation. RESULTS: Through the compilation of information from 203 articles, we have systematized knowledge on the structure and degradation of 16 major types of plant polysaccharides to form a graphical overview. As a case example, we have combined this with a list of 188 genes coding for carbohydrate-active enzymes from Aspergillus niger, thus forming an analysis framework, which can be queried. Combination of this information network with gene expression analysis on mono- and polysaccharide substrates has allowed elucidation of concerted gene expression from this organism. One such example is the identification of a full set of extracellular polysaccharide-acting genes for the degradation of oat spelt xylan. CONCLUSIONS: The mapping of plant polysaccharide structures along with the corresponding enzymatic activities is a powerful framework for expression analysis of carbohydrate-active enzymes. Applying this network-based approach, we provide the first genome-scale characterization of all genes coding for carbohydrate-active enzymes identified in A. niger.     

Enzymic degradation of the mycobacterial O-methyl-D-glucose polysaccharide by a Rhizopus-mold alpha amylase, an enzyme active on 6-O-methyl-amylo-oligosaccharides

An enzyme activity that catalyzes hydrolysis of an alpha-(1----4)-linked 6-O-methyl-D-glucan was detected in, and purified from, Rhizopus oryzae mold. The enzyme acts like an alpha amylase and digests unmodified amylo-oligosaccharides 10 to 15 times as fast as it does the 6-O-methyl and 6-deoxy derivatives. When the limit product obtained by digesting the mycobacterial O-methyl-D-glucose polysaccharide with pancreatic alpha amylase and Aspergillus glucoamylase was further digested with the Rhizopus alpha amylase, di-, tri-, and tetra-saccharide fragments composed of alpha-(1----4)-linked 6-O-methyl-D-glucose were released. The rest of the molecule was recovered as oligosaccharides terminated by two, or three, alpha-(1----4)-linked 6-O-methyl-D-glucose residues.     

Fungal degradation of calcium-, lead- and silicon-bearing minerals

The aim of this study was to examine nutritional influence on the ability of selected filamentous fungi to mediate biogenic weathering of the minerals, apatite, galena and obsidian in order to provide further understanding of the roles of fungi as biogeochemical agents, particularly in relation to the cycling of metals and associated elements found in minerals. The impact of three organic acid producing fungi (Aspergillus niger, Serpula himantioides and Trametes versicolor) on apatite, galena and obsidian was examined in the absence and presence of a carbon and energy source (glucose). Manifestation of fungal weathering included corrosion of mineral surfaces, modification of the mineral substrate through transformation into secondary minerals (i.e. crystal formation) and hyphal penetration of the mineral substrate. Physicochemical interactions of fungal metabolites, e.g. H⁺ and organic acids, with the minerals are thought to be the primary driving forces responsible. All experimental fungi were capable of mineral surface colonization in the absence and presence of glucose but corrosion of the mineral surface and secondary mineral formation were affected by glucose availability. Only S. himantioides and T. versicolor were able to corrode apatite in the absence of glucose but none of the fungi were capable of doing so with the other minerals. In addition, crystal formation with galena was entirely dependent on the availability of glucose. Penetration of the mineral substrates by fungal hyphae occurred but this did not follow any particular pattern. Although the presence of glucose in the media appeared to influence positively the mineral penetrating abilities of the fungi, the results obtained also showed that some geochemical change(s) might occur under nutrient-limited conditions. It was, however, unclear whether the hyphae actively penetrated the minerals or were growing into pre-existing pores or cracks.     

Fungal degradation of lipophilic extractives in eucalyptus globulus wood

Solid-state fermentation of eucalypt wood with several fungal strains was investigated as a possible biological pretreatment for decreasing the content of compounds responsible for pitch deposition during Cl2-free manufacture of paper pulp. First, different pitch deposits were characterized by gas chromatography (GC) and GC-mass spectrometry (MS). The chemical species identified arose from lipophilic wood extractives that survived the pulping and bleaching processes. Second, a detailed GC-MS analysis of the lipophilic fraction after fungal treatment of wood was carried out, and different degradation patterns were observed. The results showed that some basidiomycetes that decreased the lipophilic fraction also released significant amounts of polar extractives, which were identified by thermochemolysis as originating from lignin depolymerization. Therefore, the abilities of fungi to control pitch should be evaluated after analysis of compounds involved in deposit formation and not simply by estimating the decrease in the total extractive content. In this way, Phlebia radiata, Funalia trogii, Bjerkandera adusta, and Poria subvermispora strains were identified as the most promising organisms for pitch biocontrol, since they degraded 75 to 100% of both free and esterified sterols, as well as other lipophilic components of the eucalypt wood extractives. Ophiostoma piliferum, a fungus used commercially for pitch control, hydrolyzed the sterol esters and triglycerides, but it did not appear to be suitable for eucalypt wood treatment because it increased the content of free sitosterol, a major compound in pitch deposits.