Rice Bran Lipase Research Articles

Optimization of 1,3-propanediol production from fermentation of crude glycerol by immobilized Bacillus pumilus

This study investigates the application of crude glycerol to the production of 1,3-propanediol by immobilized cells of Bacillus pumilus. This is a novel application of a naturally occurring producer obtained from a wastewater storage pond in Thailand. Crude glycerol was obtained through the methanolysis of palm oil, which was catalyzed using rice bran lipase. Ten components of the fermentation medium were screened using a Plackett-Burman design. The statistical significance of the results was determined using multiple linear regression with a backward elimination approach. The significance level was set to 5 % (p < 0.05). Only crude glycerol, (NH4)2SO4, MgSO4, and CaCl2 significantly affected 1,3-propanediol production by immobilized B. pumilus. Furthermore, preliminary screenings of environmental conditions used for 1,3-propanediol production were conducted using a Plackett-Burman design. The results showed that the temperature, time, and quantity of immobilized cells were factors that significantly affected 1,3-propanediol yield. Therefore, the quantities of crude glycerol, (NH4)2SO4, MgSO4, and CaCl2 and the temperature, time, and quantity of immobilized cells were optimized using response surface methodology based on a Box-Behnken design. The model predicted a maximum 1,3-propanediol yield of 45.68 g/L with the following conditions: 60 g/L crude glycerol, 5 g/L (NH4)2SO4, 0.55 g/L MgSO4, 0.05 g/L CaCl2, a fermentation duration of 101 h, and a temperature of 25 °C, with 250 g of immobilized cells. The validation trials confirmed a production level of 44.12 ± 1.81 g/L, indicating a 2.86-fold production increase relative to the control group. Overall, this study demonstrates the potential of using crude glycerol as a substrate to improve the yields of 1,3-propanediol produced by B. pumilus.

Bound lipase: an important form of lipase in rice bran (Oryza sativa)

Rice bran residue possessed a steady lipase activity ((26.68 ± 3.69)%) after its endogenous lipase was extracted continuously by phosphate buffer solution (PBS) for 24 h. Therefore, the aim of this research was to explore whether there exist any bound lipases in rice bran (Oryza sativa). Three physical treatments (grinding, homogenizing and ultrasound crush) and 6 enzymatic treatments (cellulase, hemicellulase, pectinase, complex cellulase, glucoamylase and α-amylase) were applied to rice bran in order to investigate this bound lipase. The relative catalytic activities of extraction supernatant and residue for pectinase group were (437.63 ± 22.54)% and (159.26 ± 2.12)%, respectively, which were significantly higher (P < 0.05) than other groups. This phenomenon demonstrated that lipase was the most likely to combine with pectin. Molecular simulation proved that pectin could combine with two rice bran lipases (lipase 315 and lipase 308) and cover the catalytic centers so as to prevent the lipases from encountering the substrate and inhibiting their catalytic activities. During combination, pectin could make the lipases more compact and reduce the solvent accessible surface area of lipases, which would make the lipases inactive to molecular interaction. In summary, part of rice bran lipase was proved to exist in bound form and combined with the pectin.

Mechanism of rice bran lipase inhibition through fermentation activity of probiotic bacteria.

Rice bran oil is known as wonder oil and it is the most important vegetable oil in Asia. Rice bran oil is extracted from bran that is the outer hard layer of rice. It is an emerging category in edible oil with a lot of nutritional properties and health benefits. Rice bran oil is heart-friendly, boosts up immunity, and prevents from other diseases occurring commonly in Pakistan. The current study aimed to stabilize rice bran oil through different probiotic isolates and to assess the nutritional content of rice bran oil after stabilization. The study was aimed to inactivate naturally occurring lipases that can hydrolyze oil into glycerol and free fatty acid which is a serious problem that gives it a rancid taste and smell. Antilipase activity was used to inactivate naturally occurring lipases that are a huge threat to the stabilization process. The fermentation process utilizes antilipase activity without affecting the nutritional value of oil. Lactobacillus strains were used for the stabilization of rice bran oil. Rice bran oil was extracted in the Soxhlet apparatus. The probiotic lab isolates Lactobacillus delbrueckii S2, Lactobacillus casei S5 and Lactobacillus plantarum S13 were applied to it to increase its shelf life and prevent oxidative rancidity. The extraction temperature of rice bran oil was maintained above 40 °C to inhibit lipase activity. Rice bran oil samples were stored at refrigeration temperature to arrest lipase activity. Probiotics maintained acidic pH to keep oil stabilization. Qualitative analysis was done to confirm rice bran oil stabilization. Determination of Free Fatty Acid (FFA) and saponification value confirmed that oxidative rancidity of rice bran oil was controlled by probiotics. FFA count was less than 10% and Saponification Value (SV) was 180. GC analysis was performed to analyze the FFA profile. Gas Chromatography results have shown 3 fatty acids. Statistical analysis has shown non-significant effect on different incubation temperatures of Lactobacillus isolates. Among the biological methods of stabilization, the use of probiotics is a novel concept and recommended for commercial application.

Purification, identification, characterization and catalytic mechanism of two lipases from rice bran (Oryza sativa)

The efficient utilization of rice bran is severely impeded because of the rapid rancidity caused by rice bran lipase, so the investigation of rice bran lipase characteristic and catalytic mechanism was urgently required. The extracted crude proteins from rice bran were purified to obtain two lipases with 16.31 times of purification fold and 10.64% of purification yield. The molecular masses of these two homologous lipases were 34929.00 Da and 34072.00 Da, respectively. Rice bran lipase showed highest catalytic activity at 40.00 °C, pH 7.50 and held good stability below 50.00 °C and at pH 7.00–7.50. Most metal ions (except Na+ and Co+) and organic solvents had significant inhibition effect (P < 0.05) on the purified lipase activity. Surfactants like Tween 80, Triton 100 and sodium dodecyl sulfonate (SDS) decreased the lipase activities significantly (P < 0.05) to 70.88%, 80.08% and 73.74% respectively and cetyltrimethyl ammonium bromide (CTAB) increased the catalytic activity significantly (P < 0.05) to 109.00%. The Ser-His-Asp residues were speculated to be the catalytic center of purified lipases by using the inhibitors (Phenylmethanesulfonyl fluoride (PMSF), diethylpyrocarbonate (DEPC) and Pepstatin) which aimed at specific amino acids and then verified by molecular docking. Therefore, blocking or destroying the Ser-His-Asp catalytic triad might be new choices to restrain the rancidity of rice bran.

Application of magnetic immobilized papain on passivated rice bran lipase

Magnetically immobilized papain is prepared by magnetic Fe3O4/P (GMA-EDGMA-St) composite carrier with the addition of 12.0 mg/mL papain, 5.0% glutaraldehyde and 4 hour reaction time. The characteristic absorption peaks of each functional group were shown by infrared light. The X-diffraction pattern showed six main diffraction peaks with a magnetization value of 37.60 emu/g. TEM and SEM showed that free papain was immobilized on the magnetic carrier with an average particle size of 196 nm. The concentration of the enzyme was 122.25 mg/g, enzyme activity recovery was 55,263 U/g, compared with the free enzyme, the magnetically immobilized papain indicated higher acid-base tolerance and thermal stability, pH tolerance increased from 7.0 to 8.0, temperature tolerance increased from 60 °C to 65 °C. The magnetically immobilized papain was added to the rice bran under the condition that every gram of rice bran is submerged in 6 g of phosphate buffer solution. The magnetically immobilized papain was 0.36 mg/g, and the passivation time was 120 min. The relative activity of lipase in rice bran was 19.93%. After repeated use eight times, the relative activity of magnetically immobilized papain remained above 72%.

Comparison of 11 rice bran stabilization methods by analyzing lipase activities

The production of rice bran oil is severely impeded because of the rapid rancidity caused by rice bran lipase. Eleven stabilization treatments including 6 heating treatments and 5 nonheating treatments were carried out in this research. Lipase activities as well as oil colors, oil compositions, and contents of vitamin E and γ-oryzanol after different treatments were investigated to evaluate the effect of stabilization and oil qualities. All the treatments had no significant influence (p > .05) on the oil compositions and γ-oryzanol contents. Among six heating treatments, autoclaving had the best stabilization effect for 10.73% lipase activity remained and other heating treatments held about 30%–35% lipase activities residual except dry heating (68.88%). Heating treatments except steam heating resulted in the significant decreases (p < .05) of oil acid values and significant increases (p < .05) of peroxide values, meanwhile six heating treatments increased oil colors. Among five nonheating treatments, ultraviolet irradiation for 18 hr and extreme low temperature (−80°C) for 72 hr were found 57.08% and 58.85% lipase activities residual, respectively. Peroxide value was significantly increased (p < .05) only by ultrasound. All nonheating treatments had little effect (p > .05) on oil acid values and color. In conclusion, ultraviolet irradiation might be a potential, convenient, and energy-saving stabilization method with high oil quality. Practical applications Rice bran has a potential for producing about 8 million tons of rice bran oil worldwide but nearly 90% rice bran was wasted every year. The processing of rice bran is impeded because of the rancidity caused by lipase, so the stabilization of rice bran is very important. This research provided a new and time-saving method for evaluating stabilization efficacy instead of long time storage. Using this new evaluating method, 11 stabilization methods were compared and methods like microwave, extrusion, and ultraviolet irradiation were considered to be suitable methods for industrial processing. In additional, ultraviolet irradiation was found to be a potential, convenient, and energy-saving stabilization method without influencing oil quality and nutrient content.

Two novel lipases purified from rice bran displaying lipolytic and esterification activities

In this study, two novel lipases, rice bran lipase 1 (RBL1) and rice bran lipase 2 (RBL2), were first identified in rice (Oryza sativa) bran. Through the purification by ammonium sulfate precipitation, ion-exchange chromatography and size-exclusion chromatography, RBL1 and RBL2 were purified to 36- and 339-fold with the final specific activity of 4.73 and 44.06 U/mg, respectively. The purified RBL1 and RBL2 had the molecular weight of 18.8 and 35.5 kDa, respectively. The Km values of RBL1 and RBL2 were 0.766 and 0.432 mM while catalytic efficiency (kcat/Km) values of RBL1 and RBL2 were 102.4 and 2559.3 s−1/mM, respectively. RBL1 and RBL2 both showed esterification activity, but had no transesterification activity. In a solvent-free system, RBL1 and RBL2 exhibited degree of esterification (ED) of 4.4% and 6.5%, respectively.These two novel lipases exerted great properties for their potentials in industrial applications. First, RBL1 and RBL2 showed both mild reaction pH of 7.0 and temperature of 35 °C and 50 °C, respectively. Secondly, they showed great tolerance to several organic solvents and detergents while RBL1 exhibited great pH stability across a very broad range of pH (pH 3–12). Lastly and most importantly, RBL1 and RBL2 both exhibited esterification activity better than a commercial lipase, Candida rugosa lipase (CRL), in a solvent-free system. In conclusion, two novel lipases, RBL1 and RBL2, are different from published native lipases in rice bran and may be alternative potential candidates of biocatalysts contributing to the development of diverse industrial application fields.

Plant Lipases: A Potential Candidate for Commercial Exploitation

Lipases (triacylglycerol acylhydrolases, EC 3.1.1.3) catalyze the hydrolysis and the synthesis of esters formed from glycerol and long-chain fatty acids by acting at explicit position on the glycerol backbone of a lipid substrate. In view of the increasing understanding of lipases and their many applications in high-value syntheses and as bulk enzymes, these enzymes are having an increasing impact on bioprocessing. Lipases occur ubiquitously in nature, but only microbial lipases are presently commercially significant on industrial and therapeutic point of view. On the other hand recently plant originated lipase has provided a great alternative to microbial lipase due to the specificity, low cost, availability and ease of purification. Despite many applications of plant lipases, there are still challenges and limitations which create a gap between the small scale use and commercial exploitation of novel lipases. This review article gives an overall idea about the occurrence of various plant lipases along with different assay, purification, inhibition and immobilization process of these lipases with a specific reference to rice bran lipase.

In situ lipase-catalyzed transesterification in rice bran for synthesis of fatty acid methyl ester

Fatty acid methyl ester (FAME) were synthesized via in situ lipase-catalyzed transesterification in rice bran without additional catalyst. With this method, FAME were synthesized directly from oil in rice bran by simply adding methanol, with the aid of rice bran lipase already existing in rice bran. The effects of temperature, molar ratio (oil in rice bran to methanol), and water content of the rice bran were investigated. The yield of FAME and the free fatty acid content were monitored as a function of reaction time. The optimum conditions were a temperature of 40 °C, a molar ratio of 1:6, and a water content of 12%. Under the optimum conditions, the FAME yield of 83.4 wt% was obtained after 12 days. To further increase the FAME yield, the transesterification was repeated using the rice bran obtained from the first transesterification. The oils in rice bran that could be converted to FAME were completely transformed throughout the repeated transesterification.

Production of Oleic Acid Ethyl Ester Catalyzed by Crude Rice Bran (Oryza sativa) Lipase in a Modified Fed-batch System: A Problem and its Solution

A fed-batch system was modified for the enzymatic production of Oleic Acid Ethyl Ester (OAEE) using rice bran (Oryza sativa) lipase by retaining the substrate molar ratio (ethanol/oleic acid) at 2.05:1 during the reaction. It resulted in an increase in the ester conversion of up to 76.8% in the first 6 h of the reaction, which was then followed by a decrease from 76.8% to 22.9% in 6 h later. The production of water in the reaction system also showed a similar trend. The water was hypothesized to lead lipase to reverse the reaction which resulted in a decrease in both (water and esters) in the last 6 h of the reac- tion. In order to overcome the problem, zeolite powder (25 and 50 mg/mL) were added into the reaction system at 5 h of the reaction. As the result, the final ester conversions increased drastically up to 90 - 95.7%. Thus, the combination of a constant substrate molar ratio (ethanol/oleic acid) during the reaction (at 2.05:1) with the addition of zeolite powder (25 and 50 mg/mL) to the reaction system at 5 h is effective for the enzymatic synthesis of OAEE. Copyright © 2015 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Protease Treatment for the Stabilization of Rice Bran: Effects on Lipase Activity, Antioxidants, and Lipid Stability

ABSTRACTRice bran lipid is rapidly made rancid by endogenous lipase enzymes. To inactivate rice bran lipase, an enzymatic hydrolytic method was developed and then compared with the thermal method. The efficiency of five proteolytic enzymes including trypsin, chymotrypsin, papain, bromelain, and Flavourzyme enzyme to stabilize rice bran was investigated. Moreover, the antioxidant content and storage stability of enzymatically stabilized rice bran (ESRB), thermally stabilized rice bran (TSRB), and raw rice bran (RRB) were studied. Trypsin, chymotrypsin, and papain showed a higher rate of hydrolysis than bromelain and Flavourzyme enzyme. After 120 min of hydrolysis, rice bran hydrolyzed by trypsin, chymotrypsin, and papain inactivated 80, 86, and 79% of lipase activity, respectively, whereas lipase activity of rice bran hydrolyzed by bromelain and Flavourzyme enzyme was higher than the initial rice bran. With a similar lipase inactivation level, the cheaper papain was used to produce ESRB. Total phenolics content of ESRB was 52.89 and 94.10% higher than in RRB and TSRB, respectively. In addition, γ‐oryzanol content in ESRB was 2.23‐ and 2.05‐fold of that in RRB and TSRB, respectively. Lipase activity of RRB increased throughout the two months of storage, whereas no change in lipase activity was observed in ESRB and TSRB. At the end of storage, free fatty acid contents of RRB, TSRB, and ESRB were 15.30, 4.67, and 3.92%, respectively. We propose enzymatic hydrolysis by papain for stabilization of rice bran with high antioxidant content and storage stability.

Effect of ethanol concentrations on rice bran protease activity and ester synthesis during enzymatic synthesis of oleic acid ethyl ester in a fed-batch system using crude rice bran (Oryza sativa) lipase

Crude rice bran lipase was used for the enzymatic synthesis of Oleic Acid Ethyl Ester (OAEE) in a fed-batch system. It was found that rice bran contains protease (4.19 U/g) and lipase (324.03 U/g). The results show that protease inhibits lipase at a low concentration of ethanol (5 μmol/ml), in which lipase esterification activity was only 45.02 U/g. However, protease activity decreased about 11 times at a higher concentration of ethanol (5–50 μmol/ml). It resulted in an increase in the esterification activity of lipase (324.03 U/g). This finding could be used for explaining the effects of ethanol on the enzymatic synthesis of OAEE using crude rice bran lipase in a fed-batch system. When the ethanol concentration in the reaction system was low (≤ 4 μmol/ml), the final OAEE conversion was only 30%. It was caused both by the inhibition of lipase by rice bran protease and by the effect of low ethanol concentration on the equilibrium position of the lipase-catalysed esterification reaction. However, the final OAEE conversion reached 76–92% when higher ethanol concentrations (12.5–50 μmol/ml) were added at initial reaction. It is suggested that the addition of higher ethanol concentrations (12.5–50 μmol/ml) into the reaction system may reduce protease activity and also increase ethanol concentration in the reaction system to be converted into OAEE.

Method of phorbol ester degradation in Jatropha curcas L. seed cake using rice bran lipase

A novel enzymatic degradation of phorbol esters (PE) in the jatropha seed cake was developed using lipase. Cihera rice bran lipase had the highest ability to hydrolyze PE, and reduced PE to a safe level after 8 h of incubation. Enzymatic degradation may be a promising method for PE degradation.

Direct measurement of rice bran lipase activity for inactivation kinetics and storage stability prediction

Rice bran is a rich source of valuable nutrients and has potential for high-value applications. Endogenous lipases catalyze the hydrolysis of rice bran oil to free fatty acids, which initiates lipid oxidation. The evaluation of the success of rice bran stabilization processes in terms of the degree of lipid oxidation and shelf-life has so far relied on the measurement of free fatty acid content over a storage period of 3–6 months. In the present study, a photometric and a titrimetric pH-stat method for direct lipase activity measurement immediately after debranning were adapted to rice bran. The photometric method was further applied to determine rice bran lipase/esterase inactivation kinetics, which are useful to optimize stabilization treatments in order to prevent overprocessing and retain maximum level of nutrients. Rice bran was heat-treated in a specialized, hermetically sealable reactor at controlled holding times (5–40 min), temperatures (70–145 °C) and moisture contents (10–20%). Temperature dependency of the lipase/esterase inactivation rate could be described by the Arrhenius equation. Empirical findings on the importance of moisture content for effective rice bran stabilization could be quantified. Furthermore, the results demonstrate the great potential of the method to predict the shelf-life of stabilized rice bran without time-consuming storage tests.

Rice (Oryza sativa) lipase: Molecular cloning, functional expression and substrate specificity

Lipases are important biocatalysts showing many interesting properties with industrial applications. Previously, different isoforms of lipases, Lipase-I and Lipase-II from rice (Oryza sativa) have been purified and characterized. Lipase-II identified as the major lipase in rice bran is designated as rice bran lipase (RBL). In this study, we report the cloning and expression of the RBL in Escherichia coli and Pichia pastoris. An exploration of expression in four different E. coli expression systems analyzed: BL21(DE3)pLysS, RIL(DE3)pLysS, Rosetta(DE3)pLysS and Origami(DE3)pLysS indicated that E. coli was not a suitable host. Expression with supplement of rare codons in Rosetta (DE3)pLysS and RIL(DE3)pLysS resulted in highest expression as insoluble inclusion bodies. The hurdles of expression in E. coli were overcome by expression as a secretory protein in P. pastoris X-33. The expression of lipase in shake flasks was optimized to achieve the maximum recombinant lipase activity of 152.6U/mL. The purified recombinant lipase had a specific activity of 998U/mg toward triacetin. The pH and temperature optimum of native and recombinant enzymes were pH 7.4 and 25±2°C, respectively. Both the lipases showed higher activity toward short chain triacylglycerol and unsaturated fatty acid enriched oils. Computational modeling and molecular docking studies reveal that the catalytic efficiency of the lipase correlates with the distance of the nucleophilic Ser175-OH and the scissile ester bond. The shorter the distance, the greater is the turnover of the substrate.

Production and Optimization of Oleic Acid Ethyl Ester Synthesis Using Lipase From Rice Bran (Oryza sativa L.) and Germinated Jatropha Seeds (Jatropha curcas L.) by Response Surface Methodology

Recently, the fatty acid ethyl ester has been synthesized in place of fatty acid methyl ester since ethanol has been more renewable. In this research, oleic acid ethyl ester (OAEE) was synthesized using germinated jatropha seeds (Jatropha curcas.L) and rice bran (Oryza sativa) as source of lipase. The objective of the research was to optimize the synthesis conditions using Response Surface Methodology. Factors, such as crude enzyme concentration, molar ratio of oleic acid to ethanol, and the reaction time, were evaluated. The results show that lipase from germinated jatropha seeds had the hydrolitic and esterifi cation activity about 6.73 U/g and 298.07 U/g, respectively. Lipase from rice bran had the hydrolitic and esterifi cation activity about 10.57 U/g and 324.03 U/g, respectively. The optimum conditions of esterifi cation reaction using germinated jatropha seed lipase as biocatalyst were crude enzyme concentration of 0.31 g/ml, molar ratio of oleic acid to ethanol of 1 : 1.81, and reaction time of 50.9 min. The optimum conditions of esterifi cation reaction using rice bran lipase were crude enzyme concentration of 0.29 g/ml, molar ratio of oleic acid to ethanol of 1 : 2.05, and reaction time of 58.61 min. The obtained amounts of OAEE were 810.77 μmole and 626.92 μmole for lipases from rice bran and germinated jatropha seed, respectively.

The structure functional catalytic activity of rice bran lipase in the presence of selenium and lithium

Rice bran lipase (RBL), an esterase (EC 3.1.1.3) is a versatile enzyme that catalyzes the hydrolysis of ester linkages, primarily in neutral lipids, such as triglycerides. The catalytic activity of RBL in the presence of selenium and lithium has been investigated. Lipase isolated from rice bran was treated with different concentrations of selenium and lithium ions and further subjected to activity determination, along with the kinetics of inhibition of RBL in conjunction with structure–function relationship of the enzyme. Both ions showed competitive inhibition of RBL activity in a concentration-dependent manner (1 μM to 1 mM). At 1 mM concentration of SeO2 and Li2SO4, the enzyme loses its activity by 78 and 71%, respectively. From the analysis of the kinetic data, the inhibition constant K i is found to be 4 μM for Li2SO4, and 1 μM for SeO2, respectively. Spectrofluorimeter analysis and far UV-CD data showed minor changes in the emission intensity and conformation of the RBL in the presence of these ions at the above concentration. The results suggest that both selenium and lithium specifically inhibit RBL by probably binding near to the catalytic site or distorting the geometry of the active site of the RBL triad.

Inhibition of rice bran lipase by azadirachtin from Azadirachta indica

AbstractBACKGROUND: Chemical constituents of the neem tree are extensively explored; the major component present in the tree is azadirachtin. Azadirachtin, a tetranortriterpenoid, is remarkable for its chemical complexity and for its biological activity. This study, for the first time, has provided information on the interaction and inhibition of rice bran lipase (RBL) by azadirachtin. RBL, an esterase, is a versatile enzyme that catalyzes the hydrolysis of ester linkages, primarily in neutral lipids such as triglycerides.RESULTS: The catalytic activity of RBL in the presence of azadirachtin has been investigated. There was a decrease in enzyme activity relative to the control at all concentrations tested. At 1 mmol L−1 concentration of azadirachtin the enzyme loses 84% of its activity. The kinetics of inhibition of RBL by azadirachtin are competitive in nature. From analysis of the kinetic data the inhibition constant Ki is found to be 0.14 mmol. Fluorescence measurements showed a gradual decrease in emission intensity; a red shift in emission maximum may be attributed to perturbation of the aromatic residues. Far‐ultraviolet circular dichroism results showed minor conformational changes.CONCLUSION: The results suggest that azadirachtin specifically inhibits and binds to RBL in bringing about inhibition with minor structural alteration. This inactivation of RBL by azadirachtin can be utilized to prevent oxidation of RBL with an ultimate goal of exploiting the potential of the plant source for producing edible‐grade oil from rice bran using a natural molecule at very low concentration. Copyright © 2009 Society of Chemical Industry

Mechanism of Inhibition of Rice Bran Lipase by Polyphenols: A Case Study with Chlorogenic Acid and Caffeic Acid

Rice bran is a byproduct obtained from the rice milling industry, and to arrest lipolysis caused by lipolytic enzyme, rice bran lipase (RBL) was inactivated by inhibitors such as polyphenols. This study describes the inhibition and interaction of enzyme with chlorogenic acid (CGA) and caffeic acid (CA). The inhibition of the enzyme was competitive in nature in both CGA and CA. The inhibition constant K(i) of the reaction was found to be 1.8 and 1.5 muM for CGA and CA, respectively. Fluorescence emission measurements indicated a decrease in the fluorescence emission intensity and a red shift in the emission maximum as these ligands concentrations are increased, indicating the minor changes in the tryptophan environment and the effect of binding that is stronger in the case of CA compared to CGA with RBL. Far UV-circular dichroic data suggest that there are no significant changes in the conformation of the enzyme as a result of binding of CGA or CA. The instability of the enzyme in the presence of these polyphenols has been indicated by decrease in apparent thermal transition temperatures of the enzyme from a control value of 60 degrees C as revealed by thermal denaturation measurements. These results demonstrate that both CGA and CA are inhibitors of RBL and bind to the enzyme through both hydrogen and hydrophobic interaction in bringing about inhibition with minor structural alterations. These inactivation phenomena of polyphenols that act as inhibitors on RBL can be utilized to prevent oxidation of the rice bran oil.

Rice bran lipase catalyzed esterification of palm oil fatty acid distillate and glycerol in organic solvent

Rice bran lipase catalyzed esterification of palm oil fatty acid distillate and glycerol in organic solvent