Production of xylanase by Aspergillus awamori on synthetic medium in shake flask cultures

Hyperproduction of exopolysaccharides by submerged mycelial culture of Ganoderma lucidum using a solid seed grown in fine-powder of wheat bran and in vitro evaluation of the antioxidant activity of the exopolysaccharides produced

To facilitate Ganoderma lucidum submerged culture and obtain high productivity, a fine powder of wheat bran was used to grow the fungus for solid-state fermentation and as solid seed for its submerged cultures. The results indicated that the optimal inoculum size was low, being 0.75 g in 250 mL-sized flasks containing 80 mL medium. The maximal exopolysaccharide concentration and biomass produced was 0.74 and 14.71 g/L, respectively, which is considerably higher than that obtained with the commonly used mycelial pellet liquid seed (0.47 and 8.56 g/L, respectively). The EPS and biomass productivity of the solid seed cultures decreased only slightly, even after a 6-month storage period. EPS produced showed higher antioxidant activity compared with that produced in the liquid seed cultures. The developed solid seed can serve as a ready-to-use inoculum for long-term use in G. lucidum submerged culture for the hyperproduction of highly bioactive EPS and biomass.

Enhanced Glucosamine Production with Actinomucor elegans Based on Stimulating Factor of Methanol

Glucosamine (GlcN) is a major and valuable component in the cell wall of fungi. In this study, the cell wall was treated via a two-stage alkali and acid process, and chitin and chitosan were fully deacetylated, partially depolymerized, and converted to GlcN oligosaccharides. Then, the oligosaccharides were analyzed by high performance liquid chromatography. The influences of Actinomucor elegans on GlcN production in a flask culture were investigated to achieve an optimum yield of GlcN. The experimental result showed that cultivation in condition of pH 6.0, 100 mL working volume (500 mL flask), 10 % (v/v) inoculum concentration, at 28 °C and 200 rpm for 6 days yielded highest dry cell weight (DCW) which was 23.43 g L(-1), with a GlcN concentration of 5.12 g L(-1). Methanol as stimulating factor was found to exert the best effect in concentration of 1.5 % (v/v). With addition of methanol into medium, the DCW increased from 23.69 to 32.42 g L(-1), leading to maximum GlcN concentration of 6.85 g L(-1) obtained. Here, the methanol addition may be useful for industrial production of GlcN, and may also be meaningful for the production of other fine chemicals by filamentous fungi.

Effect of cultivation pH and agitation rate on growth and xylanase production by Aspergillus oryzae in spent sulphite liquor

The effects of cultivation pH and agitation rate on growth and extracellular xylanase production by Aspergillus oryzae NRRL 3485 were investigated in bioreactor cultures using spent sulphite liquor (SSL) and oats spelts xylan as respective carbon substrates. Xylanase production by this fungus was greatly affected by the culture pH, with pH 7.5 resulting in a high extracellular xylanase activity in the SSL-based medium as well as in a complex medium with xylan as carbon substrate. This effect, therefore, was not solely due to growth inhibition at the lower pH values by the acetic acid in the SSL. The xylanase activity in the SSL medium peaked at 199 U ml(-1) at pH 7.5 with a corresponding maximum specific growth rate of 0.39 h(-1). By contrast, the maximum extracellular beta-xylosidase activity pf 0.36 U ml(-1) was recorded at pH 4.0. Three low molecular weight xylanase isozymes were secreted at all pH values within the range of pH 4-8, whereas cellulase activity on both carbon substrates was negligible. Impeller tip velocities within the range of 1.56-3.12 m s(-1) had no marked effect, either on the xylanase activity, or on the maximum volumetric rate of xylanase production. These results also demonstrated that SSL constituted a suitable carbon feedstock as well as inducer for xylanase production in aerobic submerged culture by this strain of A. oryzae.

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.

Restructuring upstream bioprocessing: technological and economical aspects for production of a generic microbial feedstock from wheat

Restructuring and optimization of the conventional fermentation industry for fuel and chemical production is necessary to replace petrochemical production routes. Guided by this concept, a novel biorefinery process has been developed as an alternative to conventional upstream processing routes, leading to the production of a generic fermentation feedstock from wheat. The robustness of Aspergillus awamori as enzyme producer is exploited in a continuous fungal fermentation on whole wheat flour. Vital gluten is extracted as an added-value byproduct by the conventional Martin process from a fraction of the overall wheat used. Enzymatic hydrolysis of gluten-free flour by the enzyme complex produced by A. awamori during fermentation produces a liquid stream rich in glucose (320 g/L). Autolysis of fungal cells produces a micronutrient-rich solution similar to yeast extract (1.6 g/L nitrogen, 0.5 g/L phosphorus). The case-specific combination of these two liquid streams can provide a nutrient-complete fermentation medium for a spectrum of microbial bioconversions for the production of such chemicals as organic acids, amino acids, bioethanol, glycerol, solvents, and microbial biodegradable plastics. Preliminary economic analysis has shown that the operating cost required to produce the feedstock is dependent on the plant capacity, cereal market price, presence and market value of added-value byproducts, labor costs, and mode of processing (batch or continuous). Integration of this process in an existing fermentation plant could lead to the production of a generic feedstock at an operating cost lower than the market price of glucose syrup (90% to 99% glucose) in the EU, provided that the plant capacity exceeds 410 m(3)/day. Further process improvements are also suggested.

Thermostable, alkalophilic and cellulase free xylanase production by Thermoactinomyces thalophilus subgroup C

Thermoactinomyces thalophilus produced cellulase free extracellular endo-1,4-beta-xylanase (EC 3.2.1.8) at 50 degrees C and pH 8.5. Maximum xylanase production was achieved in fermentation medium using birchwood xylan as substrate after 96 h of growth at 50 degrees C. Other agricultural substrates such as wheat bran, wheat straw, sugarcane bagasse and cornstover produced less xylanase. The crude enzyme preparation from mutant T. thalophilus P2 grown under optimised fermentation conditions showed no cellulase contamination and maximum xylanase activity of 42 U/ml at 65%deg;C and pH 8.5-9.0. This enzyme with initial xylanase activity of 42 U/ml was found thermostable up to 65 degrees C and retaining 50% of its activity after its incubation for 125 min at 65 degrees C.

Influence of the process parameters on the morphology and enzyme production of Aspergilli

Several papers have been published dealing with various fungi to determine their morphology, enzyme production or process performance. However, no publication considered all of these aspects simultaneously. In the case of the production of xylanase by Aspergillus awamori the interrelationship of various key parameters are investigated. The influence of the reactor type (shake flasks, stirred tank and airlift tower loop reactor), the medium composition (semisynthetic and complex medium with wheat bran of different sizes, respectively as well as different concentrations of phosphate), and the specific power input (stirrer speed) on the growth, morphology, physiology, and productivity of the fungus are investigated. The results reveal a complex interrelationship which explains why the published results are contradictory. Without considering all of the relevant parameters, it is not possible to make general conclusions.