Scytalidium Acidophilum Research Articles

Conversion of Potato Peel Waste to Single Cell Protein by an Acidophilic Fungus

The aim of this research was to convert potato peel waste (PPW) to single cell protein (SCP), and to extract valuable phenolic compounds from the spent medium. PPW is an abundant by-product of potato processing industry, consisting mostly of starch, fibre and protein in a form of watery sludge. The PPW from a chip manufacturing plant was pre-treated with sulphuric acid, and used as a substrate for an acidophilic Scytalidium acidophilum fungus under non-aseptic conditions. The produced SCP had a promising amino acid composition to be used in animal feed. Phenolic compounds were not recovered from the spent medium, most likely due to the low pH in the medium. The present findings suggest that PPW is a suitable raw material for acidophilic SCP production, whilst the extraction of phenolic acids would require milder cultivation conditions or separation before pre-treatments of SCP production. The BOD5 of the PPW was reduced by in 98% due to fungal cultivation. Thus the feed production also served as an efficient means for reduction of organic load in the PPW.

Structural insights into the acidophilic pH adaptation of a novel endo-1,4-β-xylanase from Scytalidium acidophilum

In this study, the crystal structure of a novel endo-1,4-β-xylanase from Scytalidium acidophilum, XYL1, was solved at 1.9 Å resolution. This is one of the few solved crystal structures of acidophilic proteins. The enzyme has the overall fold typical to family 11 xylanases. Comparison of this structure with other homologous acidophilic, neutrophilic and alkalophilic xylanases provides additional insights into the general features involved in low pH adaptation (stability and activity). Several sequence and structure modifications appeared to be responsible for the acidophilic characteristic: (a) the presence of an aspartic acid H bonded to the acid/base catalyst (b) the nature of specifically conserved residues in the active site (c) the negative potential at the surface (d) the decreased number of salt bridges and H bonds in comparison with highly alkaline enzymes.

Xylanase XYL1p from Scytalidium acidophilum: Site-directed mutagenesis and acidophilic adaptation

The role of residues Asp60, Tyr35 and Glu141 in the pH-dependent activity of xylanase XYL1p from Scytalidium acidophilum was investigated by site-directed mutagenesis. These amino acids are highly conserved among the acidophilic family 11 xylanases and located near the catalytic site. XYL1p and its single mutants D60N, Y35W and E141A and three combined mutants DN/YW, DN/EA and YW/EA were over-expressed in Pichia pastoris and purified. Xylanase activities at different pH’s and temperatures were determined. All mutations increased the pH optimum by 0.5–1.5 pH units. All mutants have lower specific activities except the E141A mutant that exhibited a 50% increase in specific activity at pH 4.0 and had an overall catalytic efficiency higher than the wild-type enzyme. Thermal unfolding experiments show that both the wild-type and E141A mutant proteins have a T m maximum at pH 3.5, the E141A mutant being slightly less stable than the wild-type enzyme. These mutations confirm the importance of these amino acids in the pH adaptation. Mutant E141A with its enhanced specific activity at pH 4.0 and improved overall catalytic efficiency is of possible interest for biotechnological applications.

Studies on diversity of foliar fungal endophytes of naturalised trees from Argentina, with a description of Haplotrichum minutissimum sp. nov

An ecological investigation of foliar endophytic fungal communities on Broussonetia papyrifera, Celtis occidentalis and Ligustrum lucidum was carried out in the natural reserve Dr. Carlos Spegazzini, Buenos Aires, Argentina. The study yielded 21 taxa. Alternaria and Xylaria were the most abundant ones and both were isolated from the three hosts. Phomopsis ligustri-vulgaris, Pycnidiella resinae, Scytalidium acidophilum, Thermomyces lanuginosus and the genus Haplotrichum are cited for the first time as endophytic microorganisms, while P. resinae, Scytalidium aff . acidophilum and T. lanuginosus are cited for the first time in Argentina. A new species, Haplotrichum minutissimum, is described.

Drought meets acid: three new genera in a dothidealean clade of extremotolerant fungi

Fungal strains isolated from rocks and lichens collected in the Antarctic ice-free area of the Victoria Land, one of the coldest and driest habitats on earth, were found in two phylogenetically isolated positions within the subclass Dothideomycetidae. They are here reported as new genera and species, Recurvomyces mirabilis gen. nov., sp. nov. and Elasticomyces elasticus gen. nov., sp. nov. The nearest neighbours within the clades were other rock-inhabiting fungi from dry environments, either cold or hot. Plant-associated Mycosphaerella-like species, known as invaders of leathery leaves in semi-arid climates, are also phylogenetically related with the new taxa. The clusters are also related to the halophilic species Hortaea werneckii, as well as to acidophilic fungi. One of the latter, able to grow at pH 0, is Scytalidium acidophilum, which is ascribed here to the newly validated genus Acidomyces. The ecological implications of this finding are discussed.

Identification, Cloning, and Expression of theScytalidium acidophilumXYL1 Gene Encoding for an Acidophilic Xylanase

We cloned XYL1, a Scytalidium acidophilum gene encoding for an acidophilic family 11 xylanase. The XYL1p protein was expressed in Pichia pastoris using the pPICZalphaA expression plasmid. The secreted protein was purified by TAXI affinity column chromatography. The purified XYL1p showed an optimum activity at pH 3.2 and 56 degrees C. The Michaelis-Menten constants were determined.

Effects of Lactobacilli and an acidophilic fungus on the production performance and immune responses in broiler chickens

Accumulated lines of evidence indicate that inactivated probiotics could have beneficial effects similar to those of live probiotics. Two strains of disrupted, cobalt-enriched, lactic acid bacteria (Lactobacillus acidophilus and Lactobacillus casei) and a disrupted fungal mycelium (Scytalidium acidophilum) were spray-mixed onto a mash basal feed, in 2 concentrations, prior to pelleting. The effects of these probiotics on production performance and immune response in broiler chickens were investigated. The production parameters, including BW, feed intake (FI), BW gain (BWG), and feed conversion ratio (FCR), were monitored weekly during a 6-wk trial. The immune response was evaluated by immunizing the birds with the antigen keyhole limpet hemocyanin (KLH) followed by a serological assay to measure blood IgA and IgG titers. Some of the production parameters were significantly improved by low L. casei (LCL; for BW and BWG), high L. acidophilus (LAH; for BW and BWG), and high fungal (FH; for BW, BWG, and FI) in comparison with the nonadditive control (NC-). However, these 3 treatments (LCL, LAH, and FH) did not enhance the measured immune responses. Instead, the titers of serum KLH-specific IgA in high L. casei (LCH) and low L. acidophilus (LAL) were significantly higher than those of NC-, 10 d after immunization. None of the probiotic treatments increased the titer of KLH-specific IgG in blood. Our results indicate that disrupted and cobalt-enriched L. acidophilus or L. casei was able to enhance production performance of broiler chickens. The fungal mycelium, S. acidophilum, when used at a high concentration, also demonstrated its potential for the first time to be used as a probiotic. In addition, the optimal concentration for administering probiotics is strain dependent. A higher dose does not always result in a better performance.

Thermal stability of an acidic inulinase from Scytalidium acidophilum

Microbial inulinases (EC 3.2.1.7 or EC 3.2.1.80) offer interesting perspectives in view of the production of the high fructose syrup and fructooligosaccharides from inulin. Among them, Heat stable inulinases are advantageous in view of controlling microbial contamination and permit the use of higher soluble inulin concentrations. Recently, we found that the acid-resistant fungus Scytalidium acidophilum showed exoinulinase (EC 3.2.1.80) activity. To evaluate its industrial potential, the thermal stability of this enzyme was investigated

Assessment of acid hydrolysates of peat as substrate for Scytalidium acidophilum ATCC 26774 fungus

AbstractThe acid‐resistant fungus Scytalidium acidophilum ATCC 26774 was cultivated in submerged fermentation in hydrolysates of Sphagnum peat moss produced with H2SO4, HCl, HNO3 and H3PO4 acids. Hydrolysis with H2SO4 produced the highest concentration of total carbohydrates and reducing sugars in the hydrolysates. However, when Scytalidium acidophilum ATCC 26774 was grown in undiluted hydrolysates, the H3PO4 medium produced the best mycelial growth. The H2SO4 medium produced the highest dry biomass concentration (3.5 g dm−3) obtained with water‐diluted, non‐supplemented peat hydrolysates. Supplementation of diluted H2SO4 hydrolysates with 3 g dm−3 yeast extract and 0.4 g dm−3 MgSO4 considerably enhanced the growth, up to 5.9 g dm−3 dry fungal biomass.The biomass composition of Scytalidium acidophilum ATCC 26774 grown in the medium which produced the best growth was determined, revealing a relatively high protein content of 37.5% of the dry mycelial weight.

Extraction of bitumens and humic substances from peat and their effects on the growth of an acid-tolerant fungus

Acid hydrolysates of peat, from which the bitumens or humic substances have been removed (“modified peats”), were employed as substrates for the growth of the acid-resistant fungus Scytalidium acidophilum (Sigler and Carmichael). The removal of either or both of these fractions from the peat produced a lower dry biomass concentration than that obtained when S. acidophilum was grown in the hydrolysates of the whole peat, even when supplemented with additional nutrients. Two fractions of the humic substances, humic and fulvic acids, were extracted from peat and incorporated into synthetic media. The humic acid fraction, up to a concentration of 0.2% at pH 2.0 and 0.37% at pH 8.0, enhanced the fungal growth, but the fulvic acid fraction inhibited it at all the concentrations tested.

Fish offal-peat compost extracts as fermentation substrate

Hydrolysates of peat-fish offal compost were used as substrate sources for the growth of the acid-tolerant fungus Scytalidium acidophilum. This fungus has been previously grown on acid peat hydrolysates, and it was expected that higher concentrations of nutrients, such as nitrogen, in the fish offal-peat compost, would enhance the fungal growth. In shake-flask experiments, culture media based on the compost hydrolysates produced 2·5 g/litre of dry fungal biomass, which was not significantly different from the concentration obtained when diluted Sphagnum peat hydrolysate was employed at the substrate source. However, it was not necessary to dilute the compost hydrolysates, as is required with the peat hydrolysates, to facilitate the growth of S. acidophilum. The potential for the compost hydrolysate to support a higher microbial growth when it is supplemented with carbohydrates is discussed.

Studies on the production of Scytalidium acidophilum biomass

The conversion of nutrient-supplemented and non-supplemented acid-extracts from peat to biomass of the acid-resistant fungus Scytalidium acidophilum is described. Yeast extract and several inorganic salts were tested as nutrient supplement to the peat extract in shake-flask experiments and in an agitated and aerated fermentor. The best results were obtained in the fermentor, with 0.3% yeast extract, which produced 6.2 g dry biomass/1 with a yield of 41% and an efficiency of 30%, at 200 rpm and 1.75 vvm in 8 days. Although higher agitation speeds appeared detrimental to the mycelial physiology, it was detected that the dissolved oxygen concentration at 200 rpm could limit the growth of S. acidophilum if higher biomass concentrations are obtained. The potential for utilizing the residual fermentation medium as a plant liquid fertilizer is reported.

Effect of inorganic supplements of n, p and k on the production of scytalidium acidophilum single cell protein

Effect of inorganic supplements of n, p and k on the production of scytalidium acidophilum single cell protein

Growth of the Acid‐Tolerant Fungus Scytalidium acidophilum as a Potential Source of Single‐Cell Protein

ABSTRACTAn acid‐tolerant fungus, Scytalidium acidophilum, was cultivated in peat extract for potential use as a single‐cell protein (SCP) source. In shake flask fermentations with a 0.3% yeast extract diluted peat extract medium, it was found that the best conditions for growth occurred at pH 2.0 and 25°C. The maximum biomass concentration was produced after 10 days, with no significant differences for agitation rates between 100 and 200 rpm. Microbial contamination was not observed in nonaseptic operations. The protein content and amino acid composition of the mycelium produced compares with those reported for S. acidophilum grown in other fermentation media. The advantages of growing S. acidophilum in acid peat extract are presented.

A new acidophilic Scytalidium.

A brown mold fungus was isolated from acid soil and from acid solutions in an industrial plant and a uranium mine. The only type of spores observed were arthroconidia. The morphology of the fungus is illustrated and it is described as a new species, Scytalidium acidophilum.