Amylase hyperproduction by deregulated mutants of the thermophilic fungus Thermomyces lanuginosus

A safe potential juice clarifying pectinase from Trichoderma viride EF-8 utilizing Egyptian onion skins

The production of a notable, safe and highly active pectinase by the local fungal strain Trichoderma viride EF-8 utilizing the abundant pigmented Egyptian onion (Allium cepa L.) skins (6.5%, w/v) was achieved in 4 days submerged fermentation (SMF) cultures, at temperature and pH of 30 °C and 4.0, respectively. The indigenously produced pectinase was partially purified by 50% batch ethanol precipitation and its general properties were studied following the standard procedures. The lyophilized enzyme preparation was free of any ochra or aflatoxins. The optimum conditions for the partially purified enzyme form were 2 mg/mL and 1% (w/v) enzyme protein and substrate (citrus pectin) concentrations, reaction pH and temperature of 7.0 and 40 °C, respectively. The results presented the low cost onion skins waste as the major substrate for the fungal pectinase production and its subsequent use in perfect fruit (apple, lemon and orange) juices clarification with remarkable stability during and after this process, which certainly enhance fruit juices processing in the tropics.

Kinetics of improved 1,4-alpha-D-glucan glucohydrolase biosynthesis from a newly isolated Aspergillus oryzae IIB-6 and parameter significance analysis by 2-factorial design

Sixteen different mould cultures viz. Aspergillus, Alternaria, Arthroderma, Trichoderma, Fusarium, Penicillium, Rhizopus and Chochliobolus were isolated from the soil samples of Qatar by serial dilution method. The preliminary screening of isolates was done by selecting initial colonies showing relatively bigger zones of starch hydrolysis on nutrient agar plates. The isolates were then subjected to secondary screening by submerged fermentation (SmF). The 1,4-α-D-glucan glucohydrolase (GGH) activity ranged from 1.906-12.675 U/ml/min. The product yield was analysed in dependence of mycelial morphology, biomass level and protein content. The isolate Aspergillus oryzae llB-6 which gave maximum enzyme production was incubated in M3 medium containing 20 g/l starch, 10 g/l lactose, 8.5 g/l yeast extract, 6 g/l corn steep liquor (CSL), 1.2 g/l MgSO₄.7H₂O, 1.3 g/l NH₄Cl, 0.6 g/l CaCl₂.2H₂O, pH 5 at 30±2°C and 200 rpm. On the basis of kinetic variables, notably Q_p (0.058±0.01^a U/g/h), Y_p/s (0.308±0.03^ab U/g) and q_p (0.210±0.032^abc U/g fungal biomass/h), A. oryzae IIB-6 was found to be a hyper producer of GGH (LSD 0.0345) compared to A. kawachii IIB-2. A noticeable enhancement in enzyme activity of over 30% was observed (13.917±1.01 U/ml/min) when the process parameters viz. cultural conditions (pH 5, incubation period 72 h) and nutritional requirements (6 g/l CSL, 9.5 g/l yeast extract, 10 g/l starch, 20 g/l lactose) were further optimized using a 2-factorial Plackett-Burman design. The model terms were found to be highly significant (HS, p≤0.05), indicating the potential utility of the culture (dof~3).

Improvement of fungal cellulase production by mutation and optimization of solid state fermentation

Spores of Aspergillus sp. SU14 were treated repeatedly and sequentially with Co(60) γ-rays, ultraviolet irradiation, and N-methyl-N'-nitro-N-nitrosoguanidine. One selected mutant strain, Aspergillus sp. SU14-M15, produced cellulase in a yield 2.2-fold exceeding that of the wild type. Optimal conditions for the production of cellulase by the mutant fungal strain using solid-state fermentation were examined. The medium consisted of wheat-bran supplemented with 1% (w/w) urea or NH(4)Cl, 1% (w/w) rice starch, 2.5 mM MgCl(2), and 0.05% (v/w) Tween 80. Optimal moisture content and initial pH was 50% (v/w) and 3.5, respectively, and optimal aeration area was 3/100 (inoculated wheat bran/container). The medium was inoculated with 25% 48 hr seeding culture and fermented at 35℃ for 3 days. The resulting cellulase yield was 8.5-fold more than that of the wild type strain grown on the basal wheat bran medium.

Mutagenesis of Aspergillus Oryzae IPT-301 to improve the production of β-Fructofuranosidase

Aspergillus oryzae IPT-301, previously reported as a β-fructofuranosidase producing microorganism, was successfully mutated using UV irradiation at 253.7 nm followed by the screening of survivors resistant to certain stress conditions. Strains were first subjected to the β-fructofuranosidase activity assay using a portion from the colony grown in Petri dish as the enzyme source. Seven mutants with β-fructofuranosidase activity values relative to the parent culture between 140 - 190% were selected from survivors grown at temperature of 40ºC or 0.018% (w/v) sodium dodecyl sulfate concentration. They were cultivated on a rotary shaker to characterize mycelium and extracellular fructosyltransferase activities. Three mutants named IPT-745, IPT-746 and IPT-748 showed the highest amount of mycelium activity whose values increased 1.5 - 1.8 fold, compared with the parent strain. It was found that more than 55% of total enzyme activity (mycelium- plus extracellular- activity) from these strains was detected in the mycelium fraction. Only one mutant, IPT-747, exceeded the amount of extracellular enzyme exhibited by the parent strain (1.5 times). This mutant also showed the highest value of total fructosyltransferase activity.

Production of beta-xylanase by a Thermomyces lanuginosus MC 134 mutant on corn cobs and its application in biobleaching of bagasse pulp

The production of hemicellulases by Thermomyces lanuginosus SK using oatspelts xylan was examined during submerged cultivation. A high level of extracellular xylanase (346+/-10 U ml(-1)) production was observed on the fifth day; however, accessory enzyme levels were low. T. lanuginosus SK was further subjected to UV and N-methyl-N-nitro-N-nitrosoguanidine mutagenesis. The T. lanuginosus MC 134 mutant showed a 1.5 fold increase in xylanase production on oatspelts xylan, compared to the wild type strain. Xylanase production was further enhanced to 3299+/-95 U ml(-1) by using corn cobs under optimized growth conditions. A reduction in xylanase production was observed in a 5 L fermenter. Also, the biobleaching efficiency of crude xylanase was evaluated on bagasse pulp, and a brightness of 46.07+/-0.05% was observed with the use of 50 U of crude xylanase per gram of pulp. This brightness was 3.6 points higher than that of the untreated samples. Reducing sugars (25.78+/-0.14 mg g(-1)) and UV-absorbing lignin-derived compound values were considerably higher in xylanase-treated samples. T. lanuginosus MC 134 has a potential application in the pulp and paper industries.

Overproduction of glucoamylase by a deregulated mutant of a thermophilic mould Thermomucor indicae-seudaticae

Thermomucor indicae-seudaticae, a glucoamylase-producing thermophilic mould, was mutagenised using nitrous acid and gamma ((60)Co) irradiation in a sequential manner to isolate deregulated mutants for enhanced production of glucoamylase. The mutants were isolated on Emerson YpSs agar containing a non-metabolisable glucose analogue 2-deoxy-D-glucose (2-DG) for selection. The preliminary screening for glucoamylase production using starch-iodine plate assay followed by quantitative confirmation in submerged fermentation permitted the isolation of several variants showing varying levels of derepression and glucoamylase secretion. The mutant strain T. indicae-seudaticae CR19 was able to grow in the presence of 0.5 g l(-1) 2-DG and produced 1.8-fold higher glucoamylase. As with the parent strain, glucoamylase production by T. indicae-seudaticae CR19 in 250-ml Erlenmeyer flasks attained a peak in 48 h of fermentation, showing higher glucoamylase productivity (0.67 U ml(-1) h(-1)) than the former (0.375 U ml(-1) h(-1)). A large-scale cultivation in 5-l laboratory bioreactor confirmed similar fermentation profiles, though the glucoamylase production peak was attained within 36 h attributable to the better control of process parameters. Although the mutant grew slightly slow in the presence of 2-DG and exhibited less sporulation, it showed faster growth on normal Emerson medium with a higher specific growth rate (0.138 h(-1)) compared to the parent strain (0.123 h(-1)). The glucoamylase produced by both strains was optimally active at 60 degrees C and pH 7.0 and displayed broad substrate specificity by cleaving alpha-1,4- and alpha-1,6-glycosidic linkages in starch, amylopectin, amylose and pullulan. Improved productivity and higher specific growth rate make T. indicae-seudaticae CR19 a useful strain for glucoamylase production.

Constitutive α-amylase producing mutant and recombinant haploid strains of thermophilic fungusThermomyces lanuginosus

Morphological, developmental and antimetabolite-resistant mutants of T. lanuginosus were characterized and used for screening with the aim to develop constitutive alpha-amylase-hyperproducing strains. The protoplast fusion of two spontaneous mutants of T. lanuginosus, characterized as asporulating and resistant to 2-deoxy-D-glucose (2DG), resulted in sporulating, 2DG sensitive heterokaryotic fusants. A recombinant haploid strain F64fB developed there from produced alpha-amylase constitutively in glucose-containing medium. Constitutive alpha-amylase-hyperproducing mutant (III8) obtained after cyclic mutagenesis and screening yielded approximately 20 fold more alpha-amylase in a glycerol-containing medium than the wild strain.