Biomedical subjects

George Szakacs

Publications and source records attributed to George Szakacs.

15 recordsLinked to original sources

PubMed2006

Fungal biosynthesis of endochitinase and chitobiase in solid state fermentation and their application for the production of N-acetyl-D-glucosamine from colloidal chitin.

The present study was directed to the production of N-acetyl-D-glucosamine using endochitinase and chitobiase from fungal cultures in solid culturing. Fifteen fungal strains were evaluated for endochitinase and chitobiase production under solid-state fermentation using agro-industrial residues, of which Penicillium aculeatum NRRL 2129 showed maximum endochitinase activity whereas Trichoderma harzianum TUBF 927 showed maximum chitobiase activity. Eleven substrates, alone and in combination with chitin, were evaluated for the enzyme production. Optimization of physico-chemical parameters such as incubation period and initial moisture content, and nutritional parameters such as chitin source, inorganic and organic nitrogen sources, were carried out. Optimization resulted in more than 3-fold increase in endochitinase production (from 3.5 to 12.53 U/g dry weight of substrate) and about 1.5-fold increase in chitobiase production (from 1.6 to 2.25 U/g dry weight of substrate). Studies on the degradation of colloidal chitin to N-acetyl-D-glucosamine showed improved efficiency when endochitinase and chitobiase were used in combination.

Acetylglucosamine↗

PubMed2006

Low genetic variation and no detectable population structure in aspergillus fumigatus compared to closely related Neosartorya species.

Aspergillus fumigatus is an anamorphic euascomycete mold with a ubiquitous presence worldwide. Despite intensive work to understand its success as a pathogen infecting immunosuppressed patients, the population dynamics and recent evolutionary history of A. fumigatus remain understudied. We examined patterns of genetic variation at three intergenic loci for 70 natural isolates from Europe, North America, South America, Asia, Africa, and Australia. The same loci were used to analyze within-population genetic variation for 33 isolates obtained from five geographic locations. Neither data set detected evidence of population differentiation or found any association between the genetic and geographic distances among these isolates. No evidence for genetic differentiation within the two A. fumigatus mating types was detected. The genetic diversity of A. fumigatus, contrasted with that of its close teleomorphic relatives, Neosartorya fischeri and Neosartorya spinosa, is remarkably low.

Aspergillus fumigatus↗

PubMed2005

Xylanase production by fungal strains on spent sulphite liquor.

Xylanase production by seven fungal strains was investigated using concentrated spent sulphite liquor (SSLc), xylan and D: -xylose as carbon substrates. An SSLc-based medium induced xylanase production at varying levels in all of these strains, with Aspergillus oryzae NRRL 3485 and Aspergillus phoenicis ATCC 13157 yielding activities of 164 and 146 U ml(-1), respectively; these values were higher than those obtained on xylan or D: -xylose with the same fungal strains. The highest xylanase activity of 322 U ml(-1) was obtained with Aspergillus foetidus ATCC 14916 on xylan. Electrophoretic and zymogram analysis indicated three xylanases from A. oryzae with molecular weights of approximately 32, 22 and 19 kDa, whereas A. phoenicis produced two xylanases with molecular weights of about 25 and 21 kDa. Crude xylanase preparations from these A. oryzae and A. phoenicis strains exhibited optimal activities at pH 6.5 and 5.0 and at 65 and 55 degrees C, respectively. The A. oryzae xylanolytic activity was stable at 50 degrees C over the pH range 4.5-10. The crude xylanase preparations from these A. oryzae and A. phoenicis strains had negligible cellulase activity, and their application in the biobleaching of hardwood pulp reduced chlorine dioxide consumption by 20-30% without sacrificing brightness.

Aspergillus↗

PubMed2005

Evidence for sexuality in the opportunistic fungal pathogen Aspergillus fumigatus.

Aspergillus fumigatus is a medically important opportunistic pathogen and a major cause of respiratory allergy. The species has long been considered an asexual organism. However, genome analysis has revealed the presence of genes associated with sexual reproduction, including a MAT-2 high-mobility group mating-type gene and genes for pheromone production and detection (Galagan et al., personal communication; Nierman et al., personal communication). We now demonstrate that A. fumigatus has other key characteristics of a sexual species. We reveal the existence of isolates containing a complementary MAT-1 alpha box mating-type gene and show that the MAT locus has an idiomorph structure characteristic of heterothallic (obligate sexual outbreeding) fungi. Analysis of 290 worldwide clinical and environmental isolates with a multiplex-PCR assay revealed the presence of MAT1-1 and MAT1-2 genotypes in similar proportions (43% and 57%, respectively). Further population genetic analyses provided evidence of recombination across a global sampling and within North American and European subpopulations. We also show that mating-type, pheromone-precursor, and pheromone-receptor genes are expressed during mycelial growth. These results indicate that A. fumigatus has a recent evolutionary history of sexual recombination and might have the potential for sexual reproduction. The possible presence of a sexual cycle is highly significant for the population biology and disease management of the species.

Amino Acid Sequence↗

PubMed2005

Comparison of phytase production on wheat bran and oilcakes in solid-state fermentation by Mucor racemosus.

Comparisons were made for phytase production using wheat bran (WB) and oilcakes as substrates in solid-state fermentation (SSF) by Mucor racemosus NRRL 1994. WB was also used as mixed substrate with oil cakes. Sesame oil cake (SOC) served as the best carbon source for phytase synthesis by the fungal strain as it gave the highest enzyme titres (30.6 U/gds). Groundnut oil cake (GOC) also produced a reasonably good quantity of enzyme (24.3 U/gds). Enzyme production on WB was surprisingly much less (almost 3.5 times less in comparison to SOC). Mixing WB with SOC (1:1 ratio) resulted in better phytase activity (32.2 U/gds). Optimization of various process parameters such as incubation time, initial moisture content and inoculum concentration was carried out using the single variable mode optimization technique. Under optimized conditions, the production of phytase reached 44.5 U/gds, which was almost 1.5-fold higher than the highest yield obtained with any individual substrate used in this study and was more than 4-fold higher than that obtained from WB.

6-Phytase↗

PubMed2005

An oligonucleotide barcode for species identification in Trichoderma and Hypocrea.

One of the biggest obstructions to studies on Trichoderma has been the incorrect and confused application of species names to isolates used in industry, biocontrol of plant pathogens and ecological surveys, thereby making the comparison of results questionable. Here we provide a convenient, on-line method for the quick molecular identification of Hypocrea/Trichoderma at the genus and species levels based on an oligonucleotide barcode: a diagnostic combination of several oligonucleotides (hallmarks) specifically allocated within the internal transcribed spacer 1 and 2 (ITS1 and 2) sequences of the rDNA repeat. The barcode was developed on the basis of 979 sequences of 88 vouchered species which displayed in total 135 ITS1 and 2 haplotypes. Oligonucleotide sequences which are constant in all known ITS1 and 2 of Hypocrea/Trichoderma but different in closely related fungal genera, were used to define genus-specific hallmarks. The library of species-, clade- and genus-specific hallmarks is stored in the MySQL database and integrated in the TrichOKey v. 1.0 - barcode sequence identification program with the web interface located on . TrichOKey v. 1.0 identifies 75 single species, 5 species pairs and 1 species triplet. Verification of the DNA-barcode was done by a blind test on 53 unknown isolates of Trichoderma, collected in Central and South America. The obtained results were in a total agreement with phylogenetic identification based on tef1 (large intron), NCBI BLAST of vouchered records and postum morphological analysis. We conclude that oligonucleotide barcode is a powerful tool for the routine identification of Hypocrea/Trichoderma species and should be useful as a complement to traditional methods.

Base Sequence↗

PubMed2005

Microbial synthesis of chitinase in solid cultures and its potential as a biocontrol agent against phytopathogenic fungus Colletotrichum gloeosporioides.

Antifungal activity of chitinase can be effectively utilized in biologic pest control strategies. Because solid-state cultivation has been termed a cost-effective means for fungal growth and metabolite production, chitinase production by Trichoderma harzianum was studied using wheat bran-based solid medium containing 1% colloidal chitin. Chitinase synthesis was found to be growth associated because maximum enzyme (5.4 U/g of dry substrate) and biomass production occurred at 72 h. Substrate moisture had a critical impact on chitinase production; five grams of medium having an initial moisture content of 68.4% when incubated for 72 h increased the enzyme yield to 9.3 U/g of dry substrate. Optimization of colloidal chitin concentration showed that improvements in chitinase yield and maximum activity were attained with a 2% (w/w) concentration. Supplementation of additional nitrogen sources also influenced enzyme production, and the best yield was obtained with yeast extract. The effect of crude chitinase on hyphal morphology of the phytopathogenic fungus Colletotrichum gloeosporioides was swelling as well as lysis of hyphal wall, depending on the age of the mycelium. Studies of pH and thermal stability showed that crude culture filtrate was active over pH 4.0-6.0 and retained about 48.2% activity after 40 min of incubation at 40 degrees C.

Biomass↗

PubMed2004

Extracellular chitinase production by Trichoderma harzianum in submerged fermentation.

Extra-cellular chitinase production by a chitinolytic fungus Trichoderma harzianum TUBF 966 using submerged fermentation was studied. Colloidal chitin (1.5% w/v) was used as sole carbon source. Maximum chitinase production (14.7 U/ml) was obtained when fermentation was carried out at 30 degrees C for 96 h using 72 h old mycelium in a medium containing colloidal chitin 1.5% (w/v) as carbon source and 0.42 (% w/v) peptone as nitrogen source (pH 5.5). Supplementation of additional carbon sources (0.75% w/v) showed no further enhancement in chitinase production while supplementation of nitrogen sources (0.42% w/v) such as peptone and tryptone in the fermentation medium showed a marked increase in production. The process parameters that controlled chitinase production by the fungus were studied and presented here.

Carbon↗

PubMed2004

Coconut oil cake--a potential raw material for the production of alpha-amylase.

Solid-state fermentation (SSF) was carried out using coconut oil cake (COC) as substrate for the production of alpha-amylase using a fungal culture of Aspergillus oryzae. Raw COC supported the growth of the culture, resulting in the production of 1372 U/gds alpha-amylase in 24 h. Process optimization using a single parameter mode showed enhanced enzyme titre, which was maximum (1827 U/gds) when SSF was carried out at 30 degrees C for 72 h using a substrate with 68% initial moisture. Supplementation with glucose and starch further enhanced enzyme titre, which was maximum (1911 U/gds) with 0.5% starch. However, maltose inhibited the enzyme production. Studies on the effect of addition of external organic and inorganic nitrogenous compounds further showed a positive impact on enzyme synthesis by the culture. Increase of 1.7-fold in the enzyme activity (3388 U/gds) was obtained when peptone at 1% concentration was added to the fermentation medium. The enzyme production was growth-related, the activity being the maximum when the fungal biomass was at its peak at 72 h. Use of COC as raw material for enzyme synthesis could be of great commercial significance. To the best of our knowledge this is the first report on alpha-amylase production using COC in SSF.

Aspergillus oryzae↗

PubMed2003

Genetic and metabolic diversity of Trichoderma: a case study on South-East Asian isolates.

We have used isolates of Trichoderma spp. collected in South-East Asia, including Taiwan and Western Indonesia, to assess the genetic and metabolic diversity of endemic species of Trichoderma. Ninety-six strains were isolated in total, and identified at the species level by analysis of morphological and biochemical characters (Biolog system), and by sequence analysis of their internal transcribed spacer regions 1 and 2 (ITS1 and 2) of the rDNA cluster, using ex-type strains and taxonomically established isolates of Trichoderma as reference. Seventy-eight isolates were positively identified as Trichoderma harzianum/Trichoderma inhamatum (37 strains) Trichoderma virens (16 strains), Trichoderma spirale (8 strains), Trichoderma koningii (3 strains), Trichoderma atroviride (3 strains), Trichoderma asperellum (4 strains), Hypocrea jecorina (anamorph: Trichoderma reesei; 2 strains), Trichoderma viride (2 strains), Trichoderma hamatum (1 strain), and Trichoderma ghanense (1 strain). Analysis of biochemical characters revealed that T. virens, T. spirale, T. asperellum, T. koningii, H. jecorina, and T. ghanense formed clearly defined clusters, thus exhibiting species-specific metabolic properties. In biochemical character analysis T. atroviride and T. viride formed partially overlapping clusters, indicating that these two species may share overlapping metabolic characteristics. This behavior was even more striking with T. harzianum/T. inhamatum where genotypes defined on the basis of ITS1 and 2 sequences overlapped significantly with adjacent genotypes in the biochemical character analysis, and four strains from the same location (Bali, Indonesia) even clustered with species from section Longibrachiatum. The data indicate that the T. harzianum/T. inhamatum group represents species with high metabolic diversity and partially unique metabolic characteristics. Nineteen strains yielded three different ITS1/2 sequence types which were not alignable with any known species. They were also uniquely characterized by morphological and biochemical characters and therefore represent three new taxa of Trichoderma.

Asia, Southeastern↗

PubMed2002

Synthesis of alpha-amylase by Aspergillus oryzae in solid-state fermentation.

Spent Brewing Grains (SBG) was evaluated for its efficacy to be used as sole carbon source for the synthesis of alpha-amylase in solid-state fermentation using a fungal strain of Aspergillus oryzae NRRL 6270. Enzyme production was superior when the culture grew on mesophilic temperatures and best yields were at 25 degrees C. At 30 degrees C, yields were almost comparable. Maximum production of alpha-amylase [6870 U/g dry substrate (gds)] was obtained when SSF was carried out at 30 degrees C for 96 h using SBG medium, which had initial moisture of 70% and was inoculated using a spore suspension containing 1 x 10(7) spores/ml. Supplementation of SBG with external carbon sources such as mono-, di and polysaccharides caused repression in enzyme synthesis by the fungal culture.

Aspergillus oryzae↗

PubMed2002

Microbial production of extra-cellular phytase using polystyrene as inert solid support.

Aspergillus ficuum TUB F-1165 and Rhizopus oligosporus TUB F-1166 produced extra-cellular phytase during solid-state fermentation (SSF) using polystyrene as inert support. Maximal enzyme production (10.07 U/g dry substrate (U/gds) for A. ficuum and 4.52 U/gds for R. oligosporus) was observed when SSF was carried out with substrate pH 6.0 and moisture 58.3%, incubation temperature 30 degrees C, inoculum size of 1.3 x 10(7) spores/5 g substrate, for 72 h for A. ficuum and with substrate pH 7.0 and moisture 58.3%, incubation temperature 30 degrees C, inoculum size of 1 x 10(6) spores/5 g substrate for 96 h for R. oligosporus. Results indicated scope for production of phytase using polystyrene as inert support.

6-Phytase↗

PubMedDate not supplied

Production of phytase by Mucor racemosus in solid-state fermentation.

Phytase production was studied by three Mucor and eight Rhizopus strains by solid-state fermentation (SSF) on three commonly used natural feed ingredients (canola meal, coconut oil cake, wheat bran). Mucor racemosus NRRL 1994 (ATCC 46129) gave the highest yield (14.5 IU/g dry matter phytase activity) on coconut oil cake. Optimizing the supplementation of coconut oil cake with glucose, casein and (NH(4))(2)SO(4), phytase production in solid-state fermentation was increased to 26 IU/g dry matter (DM). Optimization was carried out by Plackett-Burman and central composite experimental designs. Using the optimized medium phytase, alpha-amylase and lipase production of Mucor racemosus NRRL 1994 was compared in solid-state fermentation and in shake flask (SF) fermentation. SSF yielded higher phytase activity than did SF based on mass of initial substrate. Because this particular isolate is a food-grade fungus that has been used for sufu fermentation in China, the whole SSF material (crude enzyme, in situ enzyme) may be used directly in animal feed rations with enhanced cost efficiency.

6-Phytase↗

PubMedDate not supplied

Solid-state fermentation for production of phytase by Rhizopus oligosporus.

Solid-state fermentation of coconut oil cake has been carried out with Rhizopus oligosporus for the production of phytase. Phytase is used commercially in the animal feed industry to improve animal performance because there is a substantial and growing interest among swine and poultry producers in the application of phytase to improve the nutritional quality in animal feeds. Demonstrated benefits include improved feed yield ratios and reduction in the environmental costs associated with the disposal of animal wastes. We report the production of extracellular phytase by R. oligosporus under solid-state fermentation using coconut oil cake as substrate. Maximal enzyme production (14.29 U/g of dry substrate) occurred at pH 5.3, 30 degrees C, and 54.5% moisture content after 96 h of incubation. The addition of extra nutrients to the substrate resulted in inhibition of product formation. The results indicate the scope for production of phytase using coconut oil cake as solid substrate without additional nutrients.

6-Phytase↗

PubMedDate not supplied

Thermostable phytase production by Thermoascus aurantiacus in submerged fermentation.

Phytases act on phytic acid, an antinutrient factor present in animal feeds, and release inorganic phosphate. We optimized the production parameters for phytase production using Thermoascus aurantiacus (TUB F 43), a thermophilic fungal culture, by submerged fermentation. A semisynthetic medium containing glucose, starch, peptone, and minerals supplemented with 3.75% (w/v) wheat bran particles was found to be the best production medium among the various combinations tried. Further supplementation of this medium with surfactants such as Tween-20 and Tween-80 considerably enhanced the enzyme yield. A maximum phytase activity (468.22 U/mL) was obtained using this production medium containing 2% (v/v) Tween-20 after 72 h of fermentation at 45 degrees C in shake-flask cultures with a rotation of 150 rpm. Herein we present details of a few of the process parameter optimizations. The phytase enzyme was found to be thermostable, and the optimal temperature for phytase activity was found to be 55 degrees C. However, 80% of the activity still remained when the temperature was shifted to 70 degrees C.

6-Phytase↗