Production of polygalacturonases by Aspergillus oryzae in stirred tank and internal- and external-loop airlift reactors

Degradation of 2,4-dichlorophenoxyacetate isopropyl amine (2,4-D IPA) by O3/AC/UV in an internally slurry airlift photo-reactor

An externally illuminated slurry airlift reactor (ALR) was used to decompose 2,4-dichlorophenoxyacetate isopropyl amine during catalytic ozonation with activated carbon. The effect of superficial gas velocity (0.05-0.15 cm/s), UV_AB irradiation (0-60 W), treatment period (10-30 min) and amount of activated carbon (0-0.8 g/l) on removal efficiency was investigated using response surface methodology (RSM) based on the Box-Behnken surface statistical design. Well-defined circulation pattern in the ALR allowed all the fluid elements to be exposed to high light intensity zone and achieve sufficient contact between the solid catalyst and the pollutant. Treatment period appeared as the most influential variable followed by the amount of activated carbon, superficial gas velocity and UV irradiation. A kinetic study was also carried out to evaluate the degradation efficiency versus the O₃, O₃/AC, O₃/UV and O₃/AC/UV combinations in which the last one had the highest impact. Efficient suspensions of AC in the ALR resulted in the high efficiency of the O₃/AC system. No significant difference was observed between the overall kinetic constants determined in O₃/AC and O₃/AC/UV systems due to the light transmission obstacle of solid suspension.

Decolorization of textile dyes in an air-lift bioreactor inoculated with Bjerkandera adusta OBR105

A new decolorizing white-rot fungus, OBR105, was isolated from Mount Odae in South Korea and identified by the morphological characterization of its fruit body and spores and partial 18s rDNA sequences. The ligninolytic enzyme activity of OBR105 was studied to characterize their decolorizing mechanism using a spectrophotometric enzyme assay. For the evaluation of the decolorization capacity of OBR105, the isolate was incubated in an erlenmeyer flask and in an airlifte bioreator with potato dextrose broth (PDB) medium supplemented with each dye. In addition, the decolorization efficiency of real textile wastewater was evaluated in an airlift bioreactor inoculated with the isolate. The isolate was identified as Bjerkandera adusta and had ligninolytic enzymes such as laccase, lignin peroxidase (LiP), and Mn-dependent peroxidase (MnP). Its LiP activity was higher than its MnP and laccase activities. B. adusta OBR105 successfully decolorized reactive dyes (red 120, blue 4, orange 16, and black 5) and acid dyes (red 114, blue 62, orange 7, and black 172). B. adusta OBR105 decolorized 91-99% of 200 mg L^-1 of each dye (except acid orange 7) within 3 days in a PDB medium at 28°C, pH 5, and 150 rpm. This fungus decolorized only 45% of 200 mg L^-1 acid orange 7 (single azo-type dye) within 3 days, and the decolorization efficiency did not increase by prolonging the cultivation time. In the air-lift bioreactor, B. adusta OBR105 displayed a high decolorization capacity, greater than 90%, for 3 acid dyes (red 114, blue 62, and black 172) and 1 reactive dye (blue 4) within 10-15 h of treatment. B. adusta OBR105 could decolorize real textile wastewater in the air-lift bioreactor. This result suggests that an air-lift reactor employing B. adusta OBR105 is a promising bioreactor for the treatment of dye wastewater.

Evaluation of agro-industrial wastes, their state, and mixing ratio for maximum polygalacturonase and biomass production in submerged fermentation

The potential of important agro-industrial wastes, apple pomace (AP) and orange peel (OP) as C sources, was investigated in the maximization of polygalacturonase (PG), an industrially significant enzyme, using an industrially important microorganism Aspergillus sojae. Factors such as various hydrolysis forms of the C sources (hydrolysed-AP, non-hydrolysed-AP, hydrolysed-AP + OP, non-hydrolysed-AP + OP) and N sources (ammonium sulphate and urea), and incubation time (4, 6, and 8 days) were screened. It was observed that maximum PG activity was achieved at a combination of non-hydrolysed-AP + OP and ammonium sulphate with eight days of incubation. For the pre-optimization study, ammonium sulphate concentration and the mixing ratios of AP + OP at different total C concentrations (9, 15, 21 g l(-1)) were evaluated. The optimum conditions for the maximum PG production (144.96 U ml(-1)) was found as 21 g l(-1) total carbohydrate concentration totally coming from OP at 15 g l(-1) ammonium sulphate concentration. On the other hand, 3:1 mixing ratio of OP + AP at 11.50 g l(-1) ammonium sulphate concentration also resulted in a considerable PG activity (115.73 U ml(-1)). These results demonstrated that AP can be evaluated as an additional C source to OP for PG production, which in turn both can be alternative solutions for the elimination of the waste accumulation in the food industry with economical returns.

Exo-pectinase production by Bacillus pumilus using different agricultural wastes and optimizing of medium components using response surface methodology

In this research, the production of exo-pectinase by Bacillus pumilus using different agricultural wastes was studied. Agricultural wastes containing pectin such as wheat bran, sugar beet pulp, sunflower plate, orange peel, banana peel, apple pomace and grape pomace were tested as substrates, and activity of exo-pectinase was determined only in the mediums containing sugar beet pulp and wheat bran. Then, effects of parameters such as concentrations of solid substrate (wheat bran and sugar beet pulp) (A), ammonium sulphate (B) and yeast extract (C) on the production of exo-pectinase were investigated by response surface methodology. First, wheat bran was used as solid substrate, and it was determined that exo-pectinase activity increased when relatively low concentrations of ammonium sulphate (0.12-0.21% w/v) and yeast extract (0.12-0.3% w/v) and relatively high wheat bran (~5-6% w/v) were used. Then, exo-pectinase production was optimized by response surface methodology using sugar beet pulp as a solid substrate. In comparison to P values of the coefficients, values of not greater than 0.05 of A and B (2) showed that the effect of these process variables in exo-pectinase production was important and that changes done in these variables will alter the enzyme activity.

The influence of sorbitol on the production of cellulases and xylanases in an airlift bioreactor

The production of cellulases and xylanases by Penicillium echinulatum in an airlift bioreactor was evaluated. In batch production, we tested media with isolated or associated cellulose and sorbitol. In fed-batch production, we tested cellulose addition at two different times, 30 h and 48 h. Higher liquid circulation velocities in the downcomer were observed in sorbitol 10 g L(-1) medium. In batch production, higher FPA (filter paper activity) and endoglucanase activities were obtained with cellulose (7.5 g L(-1)) and sorbitol (2.5 g L(-1)), 1.0 U mL(-1) (120 h) and 6.4 U m L(-1) (100 h), respectively. For xylanases, the best production condition was cellulose 10 g L(-1), which achieved 5.5 U mL(-1) in 64 h. The fed-batch process was favorable for obtaining xylanases, but not for FPA and endoglucanases, suggesting that in the case of cellulases, the inducer must be added early in the process.

Production of polygalacturonases by Aspergillus section Nigri strains in a fixed bed reactor

Polygalacturonases (PG) are pectinolytic enzymes that have technological, functional and biological applications in food processing, fruit ripening and plant-fungus interactions, respectively. In the present, a microtitre plate methodology was used for rapid screening of 61 isolates of fungi from Aspergillus section Nigri to assess production of endo- and exo-PG. Studies of scale-up were carried out in a fixed bed reactor operated under different parameters using the best producer strain immobilised in orange peels. Four experiments were conducted under the following conditions: the immobilised cells without aeration; immobilised cells with aeration; immobilised cells with aeration and added pectin; and free cells with aeration. The fermentation was performed for 168 h with removal of sample every 24 h. Aspergillus niger strain URM 5162 showed the highest PG production. The results obtained indicated that the maximum endo- and exo-PG activities (1.18 U·mL⁻¹ and 4.11 U·mL⁻¹, respectively) were obtained when the reactor was operating without aeration. The microtitre plate method is a simple way to screen fungal isolates for PG activity detection. The fixed bed reactor with orange peel support and using A. niger URM 5162 is a promising process for PG production at the industrial level.