Xylanase ofChaetomium cellulolyticum: Its nature of production and hydrolytic potential

Optimisation of Xylanase–Pectinase Cocktail Production with Bacillus amyloliquefaciens ADI2 Using a Low-Cost Substrate via Statistical Strategy

An effective statistical tool for increasing and boosting the production of xylanase and pectinase by Bacillus amyloliquefaciens ADI2 during submerged fermentation (SmF) appears to be the response of surface methodology (RSM) using the central composite design (CCD). Optimum production was achieved under fermentation conditions of a temperature of 28 °C, pH of 8.38, inoculum size of 4% (w/v) and agitation speed of 94 rpm for 48 h. The experimental responses demonstrated a near agreement with the expected responses under optimum conditions of independent variables, suggesting the model’s validity. The optimised CCD model had a 1.34-fold, 159 ± 6 U/mL greater xylanase and 5.96-fold, 205 ± 9 U/mL greater pectinase production than the one factor at a time (OFAT) approach. The production of concurrent enzymes of xylanase–pectinase resulted in a ratio of 1:1.3.

Modulating the production of xylanase by Bacillus pumilus BS131 through optimization using waste fiber sludge

In recent days, cheapest alternative carbon source for fermentation purpose is desirable to minimize production cost. Xylanases have become attractive enzymes as their potential in bio-bleaching of pulp and paper industry. The objective of the present study was to identify the potential ability on the xylanase production by locally isolated Bacillus pumilus BS131 by using waste fiber sludge and wheat bran media under submerged fermentation. Culture growth conditions were optimized to obtain significant amount of xylanase. Maximum xylanase production was recorded after 72 hours of incubation at 30 °C and 7 pH with 4.0% substrate concentration. In the nutshell, the production of xylanase using inexpensive waste fiber sludge and wheat-bran as an alternative in place of expensive xylan substrate was more cost effective and environment friendly.

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.

Synthesis of sterigmatocystin on a chemically defined medium by species of Aspergillus and Chaetomium

Sterigmatocystin (ST) is a secondary metabolite and a principal mycotoxin known to be produced by over 30 species of filamentous fungi. It is also one of the late intermediates in aflatoxin biosynthesis. We have tested the ability of 7 species of Aspergillus, including 4 strains of A. versicolor, one species of Bipolaris, and two species of Chaetomium, to produce ST on a sucrose-salts-phenylalanine defined medium as well as on three complex substrates. Highest ST production in our survey was by a strain of A. versicolor grown on wheat, whereas, the highest ST production on defined medium was by C. cellulolyticum. To our knowledge, this is the first report of ST production by C. cellulolyticum on any substrate. In precursor feeding studies, resting cultures of wild type A. nidulans and A. versicolor were unable to biotransform O-methylsterigmatocystin (OMST), the last known intermediate in aflatoxin biosynthesis. These results suggest that ST is the end product of polyketide metabolism in the strains tested.

Interference of the detergent Tween 80 in protein assays

The nonionic detergent Tween 80, which has been widely used to stimulate protein secretion in bacterial and fungal systems, caused interferences in three protein determination methods. The OD595 developed in the Coomassie blue dye-binding assay with a variety of purified proteins in the presence of Tween 80 was 1.6 to 3.4 times greater than that observed without detergent. These differences could not be attributed totally to the rapid color development in the assay with Tween 80 alone. Crude concentrated extracellular bacterial proteins shaken overnight with Tween 80 yielded an altered fractionation pattern on size exclusion chromatography and 10-fold increased color with an absorption spectrum in the dye-binding assay different from that of bacterial proteins shaken without detergent. In the bicinchoninic acid method, the detergent caused a 2- to 3-fold increase in OD562 due largely to contaminating peroxides which could be removed by treatment with catalase. In the Folin phenol method, the detergent caused a slight precipitate, but residual interference was not detectable in filtered assay mixtures.