Biodegradation of alkanolamines in batch and packed-bed reactors using free laccase and sol-gel laccase

Alkanolamine is commonly used in natural gas processing plant for carbon dioxide removal from natural gas. Alkanolamine may incidentally release and contaminate the surrounding soil and water due to plant operational failure or irresponsible related activities. Thus, the application of laccase for biodegradation of alkanolamine, which has not been reported so far, carried out in batch (shake flask) and continuous (packed-bed) reactors was investigated. Though, biodegradation using laccase may offer many advantages, the free laccase (FL) itself is unstable, cannot be reused and poor of thermal and storage stability. The sol-gel laccase (SGL), i.e. SOLAC04 was therefore synthesized by manipulating triethylamine (TEA) concentration (which was used as a gelating agent), laccase loading (LL), agitation conditions (with or without sonication), and experimental procedures (one-step or two-step) towards obtaining a higher laccase catalytic activity and stability. The SOLAC04 synthesized using two-step procedure, TEA (0.1 mL), laccase loading, LL (5 mg/mL) and without sonication had the highest laccase catalytic activity and stability as compared to other synthesized by SGL samples. This result suggested that the entrapment in silica matrix provided an additional framework for the preservation of an active laccase conformation at higher temperature and long storage duration. The biodegradation of alkanolamines: diethanolamine (DEA), ethanolamine and N-methylethanolamine was carried out in batch reactor using both FL and SGL; and optimized using response surface methodology. The results showed that the biodegradation efficiency (μ) and biodegradation rate of DEA using SOLAC04 was higher than other alkanolamines and observed to be higher compared to FL. The μ of DEA in batch reactor using FL and SOLAC04, respectively reached an optimum value at 50 °C and 40 °C. The μ of DEA increased with increasing dosage (Ds) of FL and SOLAC04. It was also revealed that the SOLAC04 are fairly stable and can be used many times. The μ of DEA remained constant at almost the same level after being reused for 5 times. The biodegradation performance and μ of DEA using FL under optimum pH of 5.8, temperature of 45.71°C, Ds of 37.14 mg, and reaction time of 42.66 minutes were 84.8 % and 0.077 mg-1, while for SGL obtained under the optimum pH of 5, temperature of 41°C, Ds of 34.01 mg, and reaction time of 57.59 minutes were 66 % and 1.11 mg-1, respectively. The μ of DEA in packed-bed reactor using SOLAC04 was optimum at pH 6, 250 mL/h and 500 ppm. The μ of DEA increased with increasing Ds of SOLAC04. These experimental results demonstrated the advantages gained from entrapment of laccase in silica matrix and the biodegradation superiority of the SGL over FL for the removal of alkanolamines. Thus, the potential of laccase especially SGL for biodegradation of the alkanolamine was finally demonstrated

The catalytic activity of laccase immobilized onto free and surfactant modified silica aerogels

The free silica aerogel (FSA) and surfactant (cetyltrimethylammonium bromide) modified silica aerogel (MSA) were synthesized and used as supports for laccase immobilization carried out through adsorption process. The results show that the MSA performed higher laccase adsorption (0.71µmol/g) as compare to FSA (0.22µmol/g). In addition, the enhancement of the catalytic activity of the MSAL was also observed. These results demonstrated that the surface modification of silica aerogel using cationic surfactant (cetyltrimethylammonium bromide) gave higher immobilized mass and catalytic activity of laccase which can be potentially used for degradation of organic micropollutants such dyes, pesticides and antibiotics

Catalytic activity and stability of encapsulated oxidoreductases for biodegradation of organic pollutants

The oxidoreductases are widely recognized for their capability to degrade organic pollutants. However, in order to enhance their biochemical stability and reusability to degrade organic pollutants especially in non-conventional solvents, the immobilization is absolutely necessary. The immobilization through encapsulation in sol-gel silica matrices was adopted based on several reports which indicated that enzymes such as lipase encapsulated in sol-gel silica matrices resulted enhanced their catalytic activity and stability. The oxidoreductases namely laccase was used exclusively in this study, while peroxidase and tyrosinase were used as comparisons. The catalytic activity of laccase and peroxidase was assayed using 2,6- dimethoxyphenol as a substrate, while the catalytic activity of the tyrosinase was assayed using L-tyrosine as a substrate. The resulted sol-gel laccase gave larger pore size (96.79 A) and strong intensity of the Fourier Transform Infrared (FTIR) spectra. The catalytic activity and stability of the sol-gel laccase and sol-gel peroxidase were proven to be significantly enhanced to 100* and 20 respectively; however the sol-gel tyrosinase was showed no measurable catalytic activity. No significant leaching of the encapsulated laccase was observed over time, suggesting that the laccase molecule were sterically confined in small pores. It was also found that the catalytic activity and stability of the sol-gel laccase could be enhanced in the presence of additives and the use of different precursors did not show any significant difference on the laccase catalytic activity. The sol-gel laccase yielded lower Km (0.72) and increased in Vmax (1779.36) compared to the free laccase. The present study also showed that the sol-gel laccase was catalytically active in non-conventional solvents (e.g. organic solvents and ionic liquids). The degradation of o-chorophenol as a model organic pollutant was also conducted in aqueous and non-conventional solvents. The High Performance Liquid Chromatography (HPLC) was used to determine the concentration of o-chlorophenol. The degree of degradation was measured by the decrease in the concentration of o-chlorophenol against its initial concentration. The results showed that the sol-gel laccase gave higher degradation than free laccase either in aqueous or non-conventional solvents. It was found that the degradation of o-chlorophenol in organic solvents either by the free or the sol-gel laccase required water and the reaction temperature significantly affected the biodegradation capability of the free and sol-gel laccase. It was also found that the sol-gel laccase could be used 10 times and fairly stable

The catalytic activity enhancement and biodegradation potential of free laccase and novel sol-gel laccase in non-conventional solvents

The catalytic activity of free laccase and a novel sol-gel laccase (SOLAC) in ionic liquids and organic solvents was demonstrated by using 2,6-dimethoxyphenol (2,6-DMP) as a substrate. The enhancement of the catalytic activity of the SOLAC was observed and compared to the free laccase in both media. The oxidative biodegradation of o-chlorophenol as a model of phenolic environmental pollutants in organic media shows that the degradation was observed only when using water pre-saturated organic solvents or reverse micelle system. The SOLAC gave higher biodegradation rate in either aqueous or organic solvents, in which the optimum temperature was observed at 40 °C for the reverse micelle system as a reaction medium. All results demonstrated the potential use of the SOLAC for biodegradation of phenolic environmental pollutants in non-conventional media

The catalytic activity of laccase immobilized in sol-gel silica

The removal potentially harmful chemicals such as substituted phenols and aromatic amines by laccase oxidative biocatalyst has been attracting interest, particularly in view of certain unsolved problems of oxidation reactions in conventional chemical process. These environmental pollutants mostly do not dissolve in an aqueous solution due to their high hydrophobicity, hence organic solvents are required to dissolve and concentrate them. The biodegradation of these pollutants using enzymatic process has been hindered by instability of enzyme in organic solvents. In order to increase enzyme stability, several methods of stabilization through immobilization and encapsulation have been reported successfully for various enzymes. Enzyme immobilization by physical entrapment has a wide benefit and may provide relatively small perturbation of the enzyme native structure and function. Therefore, in afford to enhance the laccase activity and stability; encapsulation of laccase by sol-gel silica method was studied. The catalytic activity of laccase immobilized in sol-gel silica was demonstrated by an enzymatic assay using 2, 6-dimethoxyphenol as a substrate. After immobilization, the laccase was proven to be active in a wider pH range and the laccase loading in sol-gel silica has a significant effect on laccase activity

Rice for Food Security: Revisiting Its Production, Diversity, Rice Milling Process and Nutrient Content

Rice is food consumed regularly and is vital for the food security of over half the world’s population. Rice production on a global scale is predicted to rise by 58 to 567 million tonnes (Mt) by 2030. Rice contains a significant number of calories and a wide variety of essential vitamins, minerals, and other nutritional values. Its nutrients are superior to those found in maize, wheat, and potatoes. It is also recognised as a great source of vitamin E and B5 as well as carbohydrates, thiamine, calcium, folate, and iron. Phytic acid and phenols are among the phenolic compounds found in rice, alongside sterols, flavonoids, terpenoids, anthocyanins, tocopherols, tocotrienols, and oryzanol. These compounds have been positively linked to antioxidant properties and have been shown to help prevent cardiovascular disease and diabetes. This review examines recent global rice production, selected varieties, consumption, ending stocks, and the composition of rice grains and their nutritional values. This review also includes a new method of paddy storage, drying, and grading of rice. Finally, the environmental impacts concerning rice cultivation are discussed, along with the obstacles that must be overcome and the current policy directions of rice-producing countries

Biodegradation of dye using free laccase and sol-gel laccase

Malachite green oxalate dyes are of synthetic origin and their environmental existence is not well understood. They are resistant to direct aerobic bacterial degradation and form potentially carcinogenic aromatic amines. This study shows that applying the oxidative processes of enzymatic treatment with free laccase and sol-gel laccase could lead to dye degradation. The degradation of dye malachite green oxalate using free laccase and sol-gel laccase, respectively were 37% and 13% at 1 hour reaction. The optimum pH for the free laccase and sol-gel laccase respectively were at pH 5 and pH 6. The optimal temperature for degradation of dye by sol-gel laccase was at 40°C. These results showed that free laccase and sol-gel laccase have good performance in the degradation of malachite green oxalate dyes

Rice for Food Security: Revisiting Its Production, Diversity, Rice Milling Process and Nutrient Content

Rice is food consumed regularly and is vital for the food security of over half the world’s population. Rice production on a global scale is predicted to rise by 58 to 567 million tonnes (Mt) by 2030. Rice contains a significant number of calories and a wide variety of essential vitamins, minerals, and other nutritional values. Its nutrients are superior to those found in maize, wheat, and potatoes. It is also recognised as a great source of vitamin E and B5 as well as carbohydrates, thiamine, calcium, folate, and iron. Phytic acid and phenols are among the phenolic compounds found in rice, alongside sterols, flavonoids, terpenoids, anthocyanins, tocopherols, tocotrienols, and oryzanol. These compounds have been positively linked to antioxidant properties and have been shown to help prevent cardiovascular disease and diabetes. This review examines recent global rice production, selected varieties, consumption, ending stocks, and the composition of rice grains and their nutritional values. This review also includes a new method of paddy storage, drying, and grading of rice. Finally, the environmental impacts concerning rice cultivation are discussed, along with the obstacles that must be overcome and the current policy directions of rice-producing countries

Biodegredation of dye using free laccase and sol-gel laccase

Malachite green oxalate dyes are of synthetic origin and their environmental existence is not well understood. They are resistant to direct aerobic bacterial degradation and form potentially carcinogenic aromatic amines. This study shows that applying the oxidative processes of enzymatic treatment with free laccase and sol-gel laccase could lead to dye degradation. The degradation of dye malachite green oxalate using free laccase and sol-gel laccase, respectively were 37% and 13% at 1 hour reaction. The optimum pH for the free laccase and sol-gel laccase respectively were at pH 5 and pH 6. The optimal temperature for degradation of dye by sol-gel laccase was at 40°C. These results showed that free laccase and sol-gel laccase have good performance in the degradation of malachite green oxalate dyes