Kinetics of Enzymatic Depolymerization of Guar Galactomannan

A comprehensive review on guar gum and its modified biopolymers: Their potential applications in tissue engineering

Guar gum (GG), as a non-exudate gum, is extracted from the seed's embryos of Cyamopsis tetragonoloba (a member of Leguminosae family). Recently, this biopolymer has received extensive attention due to its low cost, notable properties, non-toxic biodegradation, ease of availability, and biocompatibility. However, disadvantages such as uncontrolled hydration rate and susceptibility to microbial attack have led many researchers to further modification of guar gum. Further modifications of guar gum heteropolysaccharide have been performed to improve properties and explore and expand its potential. The favorable biostability, improved solubility, and swelling, increased pH sensitivity, and good antibacterial and antioxidant properties indicate the significant advantages of the modified gum structures with different functional groups. In this review, the rapid growth in research on GG derivatives-based materials has been discovered. Besides, the production methods of GG and its derivatives have been discussed in tissue engineering and regenerative medical. Consequently, this review highlights the advances in the production of guar-based products to outline a promising future for this biopolymer by changing its properties and expanding its applications in potential targets.

Membrane reactor for enzymatic depolymerization – a case study based on protein hydrolysis

The efficiency of enzymatic depolymerization in a membrane reactor was investigated. The model analysis was performed on bovine serum albumin hydrolysis reaction led by three different enzymes, for which kinetic equations have different forms. Comparing to a classic reactor, the reaction yield turns out to be distinctly higher for all types of kinetics. The effect arises from increasing (thanks to the proper selectivity of the applied membrane) the concentration of reagents in the reaction volume. The investigations indicated the importance of membrane selectivity election, residence time and at non-competitive inhibition the substrate (biopolymer) concentration in feed stream. Presented analysis is helpful in these parameters choice for enzymatic hydrolysis of different biopolymers.

Partially hydrolyzed guar gum as a potential prebiotic source

Guar galactomannan was enzymatically hydrolyzed to obtain partially hydrolyzed guar gum which can be utilized as prebiotic source. In present study, growth of probiotics (Lactic Acid Bacteria strains) were studied with glucose, partially hydrolyzed guar gum and native guar gum. All the six strains were galactose &/or mannose positive using the API CHl 50 test. Almost all these strains showed an ability to assimilate partially hydrolyzed guar gum with respect to increase in optical density and viable cell count with concomitant decrease in the pH of the growth medium. Streptococcus thermophilus MD2 exhibited higher growth (7.78 log cfu/ml) while P. parvulus AI1 showed comparatively less growth (7.24 log cfu/ml) as compared to used lactobacillus and Weissella strains. Outcomes of the current study suggest that partially hydrolyzed guar can be considered as potential prebiotic compound that may further stimulate the growth of potentially probiotic bacteria or native gut microflora.

Ultrasound assisted enzymatic depolymerization of aqueous guar gum solution

The present work investigates the effectiveness of application of low intensity ultrasonic irradiation for the intensification of enzymatic depolymerization of aqueous guar gum solution. The extent of depolymerization of guar gum has been analyzed in terms of intrinsic viscosity reduction. The effect of ultrasonic irradiation on the kinetic and thermodynamic parameters related to the enzyme activity as well as the intrinsic viscosity reduction of guar gum using enzymatic approach has been evaluated. The kinetic rate constant has been found to increase with an increase in the temperature and cellulase loading. It has been observed that application of ultrasound not only enhances the extent of depolymerization but also reduces the time of depolymerization as compared to conventional enzymatic degradation technique. In the presence of cellulase enzyme, the maximum extent of depolymerization of guar gum has been observed at 60 W of ultrasonic rated power and ultrasonic treatment time of 30 min. The effect of ultrasound on the kinetic and thermodynamic parameters as well as the molecular structure of cellulase enzyme was evaluated with the help of the chemical reaction kinetics model and fluorescence spectroscopy. Application of ultrasound resulted in a reduction in the thermodynamic parameters of activation energy (Ea), enthalpy (ΔH), entropy (ΔS) and free energy (ΔG) by 47%, 50%, 65% and 1.97%, respectively. The changes in the chemical structure of guar gum treated using ultrasound assisted enzymatic approach in comparison to the native guar gum were also characterized by FTIR. The results revealed that enzymatic depolymerization of guar gum resulted in a polysaccharide with low degree of polymerization, viscosity and consistency index without any change in the core chemical structure which could make it useful for incorporation in food products.

Optimization of enzymatic hydrolysis of guar gum using response surface methodology

Guar gum is a polysaccharide obtained from guar seed endosperm portion. Enzymatically hydrolyzed guar gum is low in viscosity and has several health benefits as dietary fiber. In this study, response surface methodology was used to determine the optimum conditions for hydrolysis that give minimum viscosity of guar gum. Central composite was employed to investigate the effects of pH (3-7), temperature (20-60 °C), reaction time (1-5 h) and cellulase concentration (0.25-1.25 mg/g) on viscosity during enzymatic hydrolysis of guar (Cyamopsis tetragonolobus) gum. A second order polynomial model was developed for viscosity using regression analysis. Results revealed statistical significance of model as evidenced from high value of coefficient of determination (R(2) = 0.9472) and P < 0.05. Viscosity was primarily affected by cellulase concentration, pH and hydrolysis time. Maximum viscosity reduction was obtained when pH, temperature, hydrolysis time and cellulase concentration were 6, 50 °C, 4 h and 1.00 mg/g, respectively. The study is important in optimizing the enzymatic process for hydrolysis of guar gum as potential source of soluble dietary fiber for human health benefits.

Rheological properties of guar galactomannan solutions during hydrolysis with galactomannanase and alpha-galactosidase enzyme mixtures

Guar galactomannan, a naturally occurring polysaccharide, is susceptible to hydrolysis by three enzymes: beta-mannosidase, beta-mannanase, and alpha-galactosidase. The beta-mannosidase cleaves a single mannose unit from the nonreducing end of the guar molecule, the beta-mannanase cleaves interior glycosidic bonds between adjacent mannose units, and the alpha-galactosidase cleaves the galactose side branches off the guar. In this study, hydrolysis of guar solutions using hyperthermopilic versions of these enzymes together in different proportions and combinations are examined. The enzymatic reactions are carried out in situ in a rheometer, and the progress of the reaction is monitored through measuring the variation in zero shear viscosity. We find the presence of alpha-galactosidase to affect the action of both beta-mannanase and beta-mannosidase with respect to solution rheology. However, this effect is more pronounced when the alpha-galactosidase and beta-mannanase or beta-mannosidase enzymes were added sequentially rather than simultaneously. This likely is the result of debranching of the guar, which facilitates attack on beta-1,4-linkages by both the beta-mannanase and the beta-mannosidase enzymes and increases hydrolytic rates by the individual enzymes. A rheology-based kinetic model is developed to estimate the reaction rate constants and interpret synergistic effects of multiple enzyme contributions. The model fits the experimental data well and reveals that both the native and the debranched guar have the same activation energy for beta-mannanase action, although debranching considerably increases the frequency of enzyme-guar interactions.