Production of inulinase by solid-state fermentation: effect of process parameters on production and preliminary characterization of enzyme preparations

Inulinase and fructooligosaccharide production from carob using Aspergillus niger A42 (ATCC 204447) under solid-state fermentation conditions

This study aimed to the production of inulinase and fructooligosaccharides (FOSs) from carob under the solid-state fermentation (SSF) conditions by using Plackett-Burman Design (PBD). Based on the results the maximum inulinase and specific inulinase activities were 249.98 U/mL and 318.29 U/mg protein, respectively. When the fructooligosaccharide (FOS) results were evaluated, the maximum values of 1,1,1-Kestopentaose, 1,1-Kestotetraose, and 1-Kestose were 182.01, 506.16, 132.16 ppm while the lowest and highest total FOS values were 179.35 and 516.66 ppm, respectively. On the other hand, it was observed that the maximum inulinase activity was found at the center points of the design. Therefore, validation fermentations were carried out at center point conditions. Subsequently, the yielded bulk enzyme extracts were partially purified using Spin-X UF membranes with 10, 30, and 50 kDa cut-off values. After purification, the maximum inulinase activity was 247.30 U/mg using a 50 kDa cut-off value. Followed by this process, the purified enzyme was used to produce FOSs and the results indicated that the maximum total FOS amount was 28,712.70 ppm. Consequently, this study successfully demonstrates that Aspergillus niger A42 inulinase produced from carob under the SSF conditions can be used in FOSs production.

Oligosaccharides production from coprophilous fungi: An emerging functional food with potential health-promoting properties

Functional foods are essential food products that possess health-promoting properties for the treatment of infectious diseases. In addition, they provide energy and nutrients, which are required for growth and survival. They occur as prebiotics or dietary supplements, including oligosaccharides, processed foods, and herbal products. However, oligosaccharides are more efficiently recognized and utilized, as they play a fundamental role as functional ingredients with great potential to improve health in comparison to other dietary supplements. They are low molecular weight carbohydrates with a low degree of polymerization. They occur as fructooligosaccharide (FOS), inulooligosaccharadie (IOS), and xylooligosaccahride (XOS), depending on their monosaccharide units. Oligosaccharides are produced by acid or chemical hydrolysis. However, this technique is liable to several drawbacks, including inulin precipitation, high processing temperature, low yields, and high production costs. As a consequence, the application of microbial enzymes for oligosaccharide production is recognized as a promising strategy. Microbial enzymatic production of FOS and IOS occurs by submerged or solid-state fermentation in the presence of suitable substrates (sucrose, inulin) and catalyzed by fructosyltransferases and inulinases. Incorporation of FOS and IOS enriches the rheological and physiological characteristics of foods. They are used as low cariogenic sugar substitutes, suitable for diabetics, and as prebiotics, probiotics and nutraceutical compounds. In addition, these oligosaccharides are employed as anticancer, antioxidant agents and aid in mineral absorption, lipid metabolism, immune regulation etc. This review, therefore, focuses on the occurrence, physico-chemical characteristics, and microbial enzymatic synthesis of FOS and IOS from coprophilous fungi. In addition, the potential health benefits of these oligosaccharides were discussed in detail.

Exo-inulinase production from Aspergillus fumigatus NFCCI 2426: purification, characterization, and immobilization for continuous fructose production

Aspergillus fumigatus was found to produce thermostable exo-inulinase (EC 3.8.1.80; 38 U/ml) on inulin-rich infusions. Exo-inulinase (14.6 U/mg) was immobilized on glutaraldehyde activated Ca-alginate beads for continuous generation of fructose by hydrolyzing sucrose, chicory, and dandelion substrates. Immobilization of enzyme was confirmed by microscopic and spectroscopic techniques. The exo-inulinase was purified using ion-exchange (1.30-folds) and size-exclusion chromatography (2.71-folds). The purified exo-inulinase showed 64 kDa band on gel and was optimally active at 60 °C and pH 6.0. Kinetic constants, Km and Vmax of purified exo-inulinase, were 5.88 mM and 1.66 µM/min, respectively, and its relative activity was found to be enhanced (125.8%) in the presence of calcium ion. Immobilized preparation was utilized for continuous generation of fructose from chicory juice (26 to 70%) and dandelion root extracts (16 to 24%) by recycling upto five cycles, respectively. In comparison to other sweeteners, such as sucrose, fructose is considered as a healthy alternative. The present study demonstrated the use of immobilized exo-inulinase in continuous generation of fructose from some underutilized plant sources that can be used in food industry. PRACTICAL APPLICATION: Thermostable exo-inulinase produced by A. fumigatus was immobilized on calcium alginate matrix and was employed for continuous hydrolysis of chicory juice and dandelion root extract for generation of fructose syrup.

Simultaneous production of amylases and proteases by Bacillus subtilis in brewery wastes

The simultaneous production of amylase (AA) and protease (PA) activity by Bacillus subtilis UO-01 in brewery wastes was studied by combining the response surface methodology with the kinetic study of the process. The optimum conditions (T=36.0°C and pH=6.8) for high biomass production (0.92g/L) were similar to the conditions (T=36.8°C and pH=6.6) for high AA synthesis (9.26EU/mL). However, the maximum PA level (9.77EU/mL) was obtained at pH 7.1 and 37.8°C. Under these conditions, a considerably high reduction (between 69.9 and 77.8%) of the initial chemical oxygen demand of the waste was achieved. In verification experiments under the optimized conditions for production of each enzyme, the AA and PA obtained after 15h of incubation were, respectively, 9.35 and 9.87EU/mL. By using the Luedeking and Piret model, both enzymes were classified as growth-associated metabolites. Protease production delay seemed to be related to the consumption of non-protein and protein nitrogen. These results indicate that the brewery waste could be successfully used for a high scale production of amylases and proteases at a low cost.

A new method to determine optimum temperature and activation energies for enzymatic reactions

A new method for determination of the optimum temperature and activation energies based on an idea of the average rate of enzymatic reaction has been developed. A mathematical model describing the effect of temperature on a dimensionless activity for enzyme deactivation following the first-order kinetics has been derived. The necessary condition for existence of the function extreme of the optimal temperature has been applied in the model. The developed method has been verified using the experimental data for inulinase from Kluyveromyces marxianus.

An efficient method for the immobilization of inulinase using new types of polymers containing epoxy groups

New glycidyl methacrylate copolymers containing different numbers of epoxy groups were synthesized and used to develop effective procedures for inulinase immobilization. The beneficial characteristics of the carriers included a high degree of crosslinking, stability at ambient temperature, an appropriate surface, and the presence of reactive epoxy groups. Some factors affecting the efficiency of immobilization of crude inulinase, including the kind and amount of carrier, the number of epoxy groups, as well as buffer pH and buffer concentration were examined. The yield of immobilization of this enzyme on the investigated type of microspheres was higher than on the commercial carrier, Eupergit^® C. After immobilization, the optimum temperature for inulinase activity shifted from 55 to 45 °C, whereas the optimum pH = 5 remained unchanged. The basic parameters of inulin hydrolysis were examined, and the possibility of applying the obtained biocatalyst in continuous conditions was tested. Inulin at a concentration of 0.5 % (w/v) was almost completely hydrolyzed to fructose (in a yield of 98 %) at a flow rate of 0.1 mL/min. A tenfold increase in the speed of flow resulted in an increase in the yield of oligosaccharides (DP2-DP6) up to ~41 % in the overall hydrolysate, as analysed by HPLC-RID and LC-ESI/MS. These results indicate that two forms of inulinase, an exo- and an endo-acting enzyme, were immobilized on our carrier. The enzyme showed good operational stability in a packed column over 28 days. There were no significant decreases in the efficiency of continuous hydrolysis during this time (about 17.4 % in comparison to its initial value).

Optimization, kinetics, and modeling of inulinase production by K. marxianus var. marxianus

Pressmud, a by-product from the sugarcane industry, was used as a carbon source for the production of inulinase in solid-state fermentation (SSF). Statistical experimental designs were employed to screen the nutrients and optimize the media composition for the production of inulinase by Kluyveromyces marxianus var. marxianus. Eighteen various nutrients were selected for preliminary screening of production medium component by Plackett-Burman design (PBD) technique. Five nutrients were found to be significant for inulinase production and they were optimized by central composite design (CCD). The optimal media components for solid-state fermentation of inulinase using pressmud were (g/gds): corn steep liquor, 0.06072; urea, 0.01916; beef extract, 0.00957; FeSO4 · 7H2O, 0.00013; K2HPO4, 0.00441. The effect of moisture content and substrate concentration was also studied. From the results it was found that a maximum inulinase activity of 288 U/gds occurs at the moisture content of 65% and substrate concentration of 10 g. The constants in the Michaelis-Menten equation were evaluated and a high R (2) value implied the fitness of the model. Artificial neural network (ANN) modeling was also employed to predict the inulinase production.

Enhanced inulinase production by Streptomyces sp. in solid state fermentation through statistical designs

In this work, inulinase was produced by solid state fermentation by Streptomyces sp. using copra waste as carbon source. The nutrients were screened by Plackett-Burman design. From the pareto chart it was found that the nutrients, namely, soya bean cake, MgSO4·7H2O and (NH4)2SO4 were found to be most significant nutrient components. Hence, these three components were selected for further optimization using central composite design (CCD) in response surface methodology (RSM). The optimum conditions were soya bean cake: 0.05711 g/gds, MgSO4·7H2O: 0.00063 g/gds and (NH4)2SO4: 0.00772 g/gds. Under these optimized conditions, the production of inulinase was found to be 131 U/gds. The constants in the Michaelis-Menten equation were evaluated and high R2 value implies the fitness of the model.

Utilization of copra waste for the solid state fermentative production of inulinase in batch and packed bed reactors

In this study, screening and optimization of nutrients for inulinase production using copra waste has been studied. Plackett-Burman Design (PBD) was employed to screen the significant nutrients for inulinase production. Response surface methodology (RSM) was used to evaluate the effects of nutrient components in the medium. The second order regression equation provides the inulinase activity as the function of K2HPO4, ZnSO4 · 7H2O and soya bean cake. The optimum conditions are: K2HPO4--0.0047 g/gds, ZnSO4 · 7H2O - 0.02677 g/gds and soya bean cake--0.06288 g/gds. At these optimized conditions, experiments were performed in packed bed bioreactor to optimize the process variables like air flow rate, packing density, particle size and moisture content. The optimum conditions were: air flow rate--0.76 L/min, packing density--38 g/L, particle size--10/14 mesh and moisture content--60%. At the optimized conditions, a maximum inulinase production of 239 U/gds was achieved.

Optimization of inulinase production by a newly isolated Aspergillus tubingensis CR16 using low cost substrates

Production of an extracellular, thermostable inulinase was carried out by a newly isolated strain of Aspergillus tubingensis CR16 using wheat bran and corn steep liquor (CSL) under solid state fermentation (SSF). Response surface methodology (RSM) involving Box Behnken design (BBD) was employed for the optimization of process parameters viz. time period of fermentation, % moisture content, inoculum size and pH of the medium. Maximum yield of inulinase was 257±11.4 U/g, obtained by inoculating 5 g of wheat bran with 10(9) spores/ml, at initial 71.2% moisture content and pH 6.1 after 103 h of fermentation along with 1358.6±0.8 U/g of invertase activity. Crude inulinase showed maximum activity at 60 °C and pH 5.0. The enzyme was found to be thermostable retaining about 90% of its activity for 4.5 h at 60 °C. Fructose was produced as an end product of inulin hydrolysis proving that the enzyme produced was exoinulinase.

Development of a solid-state fermentation process for production of an alpha amylase with potentially interesting properties

Ca-independency with potential activity and stability at low pH are among the most interesting characteristics of alpha-amylase in starch industry. In this attempt the synergetic effect of low pH on activity of crude Ca-independent alpha-amylase isolated from a native Bacillus sp. KR-8104 in solid-state fermentation (SSF) was studied using wheat bran (WB) as a substrate. The effects of different parameters including moisturizing agents, solid substrate to moisture ratio, particle size, incubation temperature and period, inoculum (v/w) and supplementation with 1% (w/w) different carbon and nitrogen sources on enzyme production were investigated. Maximum enzyme production of 140U/g dry fermented substrate was obtained from wheat bran moistened with tap water at a ratio of 1:1.5 and supplemented with 1% (w/w) NH(4)NO(3) and 1% (w/w) lactose after 48h incubation at 37 degrees C. Even though the production of alpha-amylase was lower at 40 and 45 degrees C, the viable cell count was higher. In addition response surface methodology (RSM) was applied to find optimum conditions of temperature and pH on crude amylase activity. Using central composite design (CCD) a quadratic mathematical model equation was derived for the prediction of enzyme activity. The results showed that the model was in good agreement with experimental results, with R(2)=0.90 (p<0.0001) and the low pH has a synergetic effect on enzyme activity at higher temperature.

Mathematical modeling of Kluyveromyces marxianus growth in solid-state fermentation using a packed-bed bioreactor

This work investigated the growth of Kluyveromyces marxianus NRRL Y-7571 in solid-state fermentation in a medium composed of sugarcane bagasse, molasses, corn steep liquor and soybean meal within a packed-bed bioreactor. Seven experimental runs were carried out to evaluate the effects of flow rate and inlet air temperature on the following microbial rates: cell mass production, total reducing sugar and oxygen consumption, carbon dioxide and ethanol production, metabolic heat and water generation. A mathematical model based on an artificial neural network was developed to predict the above-mentioned microbial rates as a function of the fermentation time, initial total reducing sugar concentration, inlet and outlet air temperatures. The results showed that the microbial rates were temperature dependent for the range 27-50 degrees C. The proposed model efficiently predicted the microbial rates, indicating that the neural network approach could be used to simulate the microbial growth in SSF.