Sushil Nagar

Production of alkali tolerant cellulase free xylanase in high levels by Bacillus pumilus SV-205

The fermentation conditions were optimized for hyper production of xylanase from Bacillus pumilus SV-205. The bacterium secretes high levels (7382.7±1200 IU/mL) of cellulase-free xylanase using wheat bran led to 21.63 fold increase in activity. A combination of yeast extract and peptone stimulated highest xylanase production (2448.0 IU/mL) as compared to other combinations. The most important characteristic of the enzyme is its high pH stability (100%) over a broad pH range of 6-11 for 24h. Thermostability studies revealed that enzyme retained 65% activity after an incubation of 2h at 60°C. The level of production is remarkable as compared to earlier reports.

Hyper production of alkali stable xylanase in lesser duration by Bacillus pumilus SV-85S using wheat bran under solid state fermentation.

High level production of an extracellular cellulase-poor alkali stable xylanase has been conceded from newly isolated Bacillus pumilus SV-85S under solid state fermentation using wheat bran as a substrate. Optimization of the fermentation conditions enhanced the enzyme production to 73,000 ± 1,000 IU/g dry substrate, which was 13.8-fold higher than unoptimized conditions (5,300 IU/g). The enzyme titre was highest after 48 h of incubation at 30°C with 1:3 ratios of substrate to moistening agent using wheat bran as a carbon source. The enzyme could be produced in significant levels by using either tap water or distilled water alone as a moistening agent. An elevated production of xylanase by B. pumilus SV-85S in the presence of wheat bran, a cheap and easily available agro-residue, in shorter duration would apparently reduce the enzyme cost substantially. The enzyme was completely stable over a broad pH (5-11) range and retained 52% of its activity at a temperature of 70°C for 30 min. The desired characteristics of this enzyme together with economic production would be important for its application in paper and pulp industry.

Enzymatic clarification of fruit juices (Apple, Pineapple, and Tomato) using purified Bacillus pumilus SV-85S xylanase

The xylanase obtained from a hyper-producer Bacillus pumilus SV-85S was purified and characterized to evaluate its potential in industrial applications. Xylanase was purified to homogeneity 25.3-fold with 63.2% recovery using cation-exchange chromatography through CMSephadex C-50. The purified xylanase showed a single band on Native-PAGE and a single peak in RP-HPLC confirming its homogeneity. The purified enzyme revealed a single band on SDS-PAGE with a molecular mass of 23.6 kDa, which was confirmed with gel filtration chromatography through Sepharose 6B. The Km and Vmax of the purified xylanase was 1.0 mg/mL and 333.3 IU/mL, respectively. The temperature and pH profiles of the purified xylanase revealed that it was thermo and alkali stable. In recent years due to the overall increase in natural fruit juice consumption, juices have become important from a consumption point of view. However, raw juice is turbid and viscous which tends to settle during storage. Therefore, it must be clarified before commercialization. The efficacy of absolutely purified xylanase was studied on juice enrichment of apples (Malus domestica), pineapples (Ananas comosus L.) and tomatos (Lycopersicum esculentum). The treatment with xylanase lead to an increased juice yield by 23.53% (apple), 10.78% (pineapple), and 20.78% (tomato) as well as having a significant effect on juice clarity by an increase of % transmittance of 22.20, 19.80, and 14.30, respectively. The turbidity and viscosity was also decreased without affecting acid neutrality significantly.

Covalent immobilization of xylanase produced from Bacillus pumilus SV‐85S on electrospun polymethyl methacrylate nanofiber membrane

Polymethyl methacrylate (PMMA) nanofiber membrane (NFM) was synthesized by an electrospinning technique. These membranes were utilized as a support for immobilization of xylanase enzyme to study its pH stability, thermal stability, and reusability. The morphology of aligned NFM was studied by optical microscopy and scanning electron microscopy. The PMMA NFM was functionalized with phenylenediamine and activated with glutaraldehyde to yield an aldehyde group on its surface for covalent immobilization of xylanase. The Fourier transform infrared analysis of the covalently immobilized xylanase confirmed that the enzyme was immobilized on PMMA NFM via amide linkages. The immobilization efficiency of covalently bound xylanase was found experimentally to be 90%. A forward shift in pH optima from 6.0–7.0 (soluble enzyme) to 7.0–9.0 (immobilized enzyme) was observed after xylanase immobilization. The pH and temperature stability of xylanase were enhanced upon its covalent immobilization. The immobilized enzyme was active on repeated use and retained ∼80% of its initial activity after 11 reaction cycles. The improved thermal and operational stability of the covalently immobilized enzyme on PMMA NFM might be advantageous for industrial applications.

Model Order Reduction of Interval Systems using Mihailov Criterion and Factor Division Method

paper presents a mixed method for reducing order of the large scale interval systems using the Mihailov Criterion and factor division method. The denominator coefficients of reduced order model is determined by using Mihailov Criterion and numerator coefficients are obtained by using Factor division method. The mixed methods are simple and guarantee the stability of the reduced model if the original system is stable. Numerical examples are discussed to illustrate the usefulness of the proposed method.

A New Algorithm for Model Order Reduction of Interval Systems

Mixed method of interval systems is a combination of classical reduction methods and stability preserving methods of interval systems. This paper proposed a new method for model order reduction of systems with uncertain parameters. The bounds on the uncertain parameters are known a priori. Two separate methods are used for finding parameters of the numerator and denominator. The numerator parameters are obtained by either of these methods such as differentiation method, factor division method, cauer second form, moment matching method or Pade approximation method. The denominator is obtained by the differentiation method in all the cases. A numerical example has been discussed to illustrate the procedures. From the above mixed methods, differentiation method and cauer second form as resulted in better approximation when compared with other methods. The errors between the original higher order and reduced order models have also been highlighted to support the effectiveness of the proposed methods.

Reducing order of large-scale systems by extended balanced singular perturbation approximation

In this paper, a simplified approach for model order reduction, based on balanced singular perturbation approximation (BSPA) technique, is explored which is applicable for linear time invariant, minimal/non-minimal continuous/discrete-time systems. An extension of BSPA technique is proposed for order reduction of unstable systems. For reduction of unstable system, a system decomposition algorithm using real Schur transformation is given to decompose the unstable system into stable and unstable parts. Reduced order model of original unstable system is obtained by reducing the decomposed stable part by BSPA technique and directly adding it to decomposed unstable part. The algorithm is illustrated with MATLAB-based computer-simulated results in both time and frequency domains.

Controller reduction by balanced approach with guaranteed closed-loop performance

This paper addresses an algorithmic approach for controller reduction problem using balanced singular perturbation approximation (BSPA) technique for unweighted cases. The controller design methods generally lead to a controller of order comparable to plant and sometimes unstable controllers. For reduction of such controllers, a controller decomposition algorithm in conjunction with BSPA technique is presented. It is shown by numerical examples that reduced order controller by balanced truncation fails for some cases to stabilize the closed-loop system whereas resulting closed-loop system with reduced order controller using BSPA is guaranteed to preserve the closed-loop system stability and H∞ performance.