Microbial α-amylases: a biotechnological perspective

This review describes pharmacologically active compounds from mushrooms. Compounds and complex substances with antimicrobial, antiviral, antitumor, antiallergic, immunomodulating, anti-inflammatory, antiatherogenic, hypoglycemic, hepatoprotective and central activities are covered, focusing on the review of recent literature. The production of mushrooms or mushroom compounds is discussed briefly.

https://downloads.hindawi.com/journals/ecam/2005/906016.pdf

The pharmacological potential of mushrooms.

The production of organic acids by fungi has profound implications for metal speciation, physiology and biogeochemical cycles. Biosynthesis of oxalic acid from glucose occurs by hydrolysis of oxaloacetate to oxalate and acetate catalysed by cytosolic oxaloacetase, whereas on citric acid, oxalate production occurs by means of glyoxylate oxidation. Citric acid is an intermediate in the tricarboxylic acid cycle, with metals greatly influencing biosynthesis: growth limiting concentrations of Mn, Fe and Zn are important for high yields. The metal-complexing properties of these organic acids assist both essential metal and anionic (e.g. phosphate) nutrition of fungi, other microbes and plants, and determine metal speciation and mobility in the environment, including transfer between terrestrial and aquatic habitats, biocorrosion and weathering. Metal solubilization processes are also of potential for metal recovery and reclamation from contaminated solid wastes, soils and low-grade ores. Such ‘heterotrophic leaching’ can occur by several mechanisms but organic acids occupy a central position in the overall process, supplying both protons and a metal-complexing organic acid anion. Most simple metal oxalates [except those of alkali metals, Fe(III) and Al] are sparingly soluble and precipitate as crystalline or amorphous solids. Calcium oxalate is the most important manifestation of this in the environment and, in a variety of crystalline structures, is ubiquitously associated with free-living, plant symbiotic and pathogenic fungi. The main forms are the monohydrate (whewellite) and the dihydrate (weddelite) and their formation is of significance in biomineralization, since they affect nutritional heterogeneity in soil, especially Ca, P, K and Al cycling. The formation of insoluble toxic metal oxalates, e.g. of Cu, may confer tolerance and ensure survival in contaminated environments. In semiarid environments, calcium oxalate formation is important in the formation and alteration of terrestrial subsurface limestones. Oxalate also plays an important role in lignocellulose degradation and plant pathogenesis, affecting activities of key enzymes and metal oxidoreduction reactions, therefore underpinning one of the most fundamental roles of fungi in carbon cycling in the natural environment. This review discusses the physiology and chemistry of citric and oxalic acid production in fungi, the intimate association of these acids and processes with metal speciation, physiology and mobility, and their importance and involvement in key fungal-mediated processes, including lignocellulose degradation, plant pathogenesis and metal biogeochemistry.

Fungal production of citric and oxalic acid: importance in metal speciation, physiology and biogeochemical processes.

The fungi-to-bacteria ratio in soil ecological concepts and its application to explain the effects of land use changes have gained increasing attention over the past decade. Four different main approaches for quantifying the fungal and bacterial contribution to microbial tissue can be distinguished: (1) microscopic methods, (2) selective inhibition, (3) specific cell membrane components and (4) specific cell wall components. In this review, the different methods were compared and we hypothesized that all these approaches result in similar values for the fungal and bacterial contribution to total microbial biomass, activity, and residues (dead microbial tissue) if these methods are evenly reliable for the estimation of fungal biomass. The fungal contribution to the microbial biomass or respiration varied widely between 2 and 95% in different data sets published over the past three decades. However, the majority of the literature data indicated that fungi dominated microbial biomass, respiration or non-biomass microbial residues, with mean percentages obtained by the different methodological approaches varying between 35 and 76% in different soil groups, i.e. arable, grassland, and forest soils and litter layers. Microscopic methods generally gave the lowest average values, especially in arable and grasslands soils. Very low ratios in fungal biomass C-to-ergosterol obtained by microscopic methods suggest a severe underestimation of fungal biomass by certain stains. Relatively consistent ratios of ergosterol to linoleic acid (18:2ω6,9) indicate that both cell membrane components are useful indicators for saprotrophic and ectomycorrhizal fungi. More quantitative information on the PLFA content of soil bacteria and the 16:1ω5 content of arbuscular mycorrhizal fungi is urgently required to fully exploit the great potential of PLFA measurements. The most consistent results have been obtained from the analysis of fungal glucosamine and bacterial muramic acid in microbial residues. Component-specific δ 13 C analyses of PLFA and amino sugars are a promising prospect for the near future.

Quantitative assessment of the fungal contribution to microbial tissue in soil

The genus Pleurotus comprises a group of edible ligninolytic mushrooms with medicinal properties and important biotechnological and environmental applications. The cultivation of Pleurotus spp is an economically important food industry worldwide which has expanded in the past few years. P. ostreatus is the third most important cultivated mushroom for food purposes. Nutritionally, it has unique flavor and aromatic properties; and it is considered to be rich in protein, fiber, carbohydrates, vitamins and minerals. Pleurotus spp are promising as medicinal mushrooms, exhibiting hematological, antiviral, antitumor, antibiotic, antibacterial, hypocholesterolic and immunomodulation activities. The bioactive molecules isolated from the different fungi are polysaccharides. One of the most important aspects of Pleurotus spp is related to the use of their ligninolytic system for a variety of applications, such as the bioconversion of agricultural wastes into valuable products for animal feed and other food products and the use of their ligninolytic enzymes for the biodegradation of organopollutants, xenobiotics and industrial contaminants. In this Mini-Review, we describe the properties of Pleurotus spp in relation to their biotechnological applications and potential.

Biotechnological applications and potential of wood-degrading mushrooms of the genus Pleurotus.

Pleurotus fruiting bodies contain the inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme a reductase-lovastatin

We have tested 380 strains of our Fungal Culture Collection (MZKIBK), for the activity of the inhibitor of HMG CoA reductase, mevinolin. All fungal strains were cultivated in a two-step submerged fermentation on selected substrates. For the first screening, samples of broth extracts were tested by TLC and positive results were further evaluated by HPLC analysis. In addition to already known microbiol producers of HMG CoA reductase inhibitors and some newly identified strains having moderate activity, we found that fungi of the basidiomycetous genus Pleurotus, especially species P. ostreatus, P. saca and P. sapidus, are an as yet unknown but promising source of the hypocholesterolaemic agent.

Screening fungi for the production of an inhibitor of HMG CoA reductase: Production of mevinolin by the fungi of the genus Pleurotus

High-performance liquid chromatographic analysis of mevinolin as mevinolinic acid in fermentation broths☆

The production of a pectolytic enzyme complex in a 10-l strirred tank bioreactor was studied using the Aspergillus niger mutant A 138. A time course of the fermentation showed that the enzyme synthesis is not associated with growth. Maximal activity was reached after 95 h and from that time on it remained constant. Redox potential and pH values proved to be valuable indicators of the initiation and end of enzyme synthesis. The specific morphology of the fungus, growing in distinct pellets with long peripheral hyphae, resulted in a very dense and viscous broth. It represented a special problem for heat and mass transfer. An attempt was made to overcome this problem by different agitation and aeration regimes. These parameters did not change the morphology but had a marked influence on enzyme synthesis. When, at the time of maximal growth rate, aeration was increased from 0.5 vvm to 1.2 vvm, and agitation from 300 rpm to 500 rpm, the depectinizing activity was doubled in comparison with the results obtained when 0.5 vvm and 300 rpm were used throughout fermentation. When more intensive agitation was employed from the beginning of the process, the depectinizing activity was lowered from 60 to 45 units/ml, together with the viscosity and polygalacturonase activity. However, at the same time, the pectin esterase and pectinlyase yields increased. The required fermentation time was reduced from 95 to 65 h.

Submerged production of pectolytic enzymes by Aspergillus niger: effect of different aeration/agitation regimes

Fungi of the genus Pleurotus were shown to produce the 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor mevinolin. Crude methanol extracts and purified inhibitor from three different species, P. sapidus, P. saca and P. ostreatus, were tested using the solubilized microsomal HMGCoA reductase from Chinese hamster ovary cells. The identity of the inhibitor was also confirmed by thin layer chromatography, high pressure liquid chromatography and mass spectroscopy.

Aleksa Cimerman

Papers

Pleurotus fruiting bodies contain the inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme a reductase-lovastatin

Screening fungi for the production of an inhibitor of HMG CoA reductase: Production of mevinolin by the fungi of the genus Pleurotus

High-performance liquid chromatographic analysis of mevinolin as mevinolinic acid in fermentation broths☆

Submerged production of pectolytic enzymes by Aspergillus niger: effect of different aeration/agitation regimes

Pleurotus fungi produce mevinolin, an inhibitor of HMG CoA reductase