STANDARDIZATION OF ALKALINE AND ENZYMATIC TECHNIQUES FOR PURIFICATION OF PROTEIN ISOLATES AND PROCESSED PRODUCTS FROM DIFFERENT VARIETIES OF RICE
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Date
2020
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Indira Gandhi Krishi Vishwavidyalaya, Raipur
Abstract
Rice is consumed as a staple food in most of the countries of the world. It is mainly a starchy food with less of proteins, lipids, minerals, etc. Consumption of unmilled rice has its own advantages and disadvantages. However, people all over the world prefer milled and well polished rice over un-milled rice or brown rice. Processing of rice grains removes the highly nutritional rice bran layer. The milled rice, otherwise known as white rice, has less of protein compared to the brown rice.
Protein isolates are prepared nowadays as protein supplements for the busy and fast moving human life. However, difficulties in the processing, cause the
availability of rice protein products less easy. Rice protein in the endosperm is associated tightly on the surface of starch granules creating difficulty in the protein removal. This is also the reason that isolation of rice starch is more costly compared to other starches. Starch is essential for its contribution of calorie to the human diet. Rice varieties differ greatly in their genetic background, granule size, composition and gelatinization which may have an effect on the properties of the isolated starches.
Ethanol is an organic compound with the chemical formula C2H5OH. The demand for ethanol has risen in recent years because of its widespread use in chemical, potable and motorfuel industries. Ethanol is produced either by synthetic chemical method or by natural fermentation. A large number of micro-organisms have the capability to convert sugars into ethanol under anaerobic conditions.
The waxy nature of rice is preferred in few parts of the world and the waxy gene has been the primary objective of selection during the domestication and subsequent diversification of the rice crop. So, selection of rice varieties using markers can be a work of help for such purposes. Increasing temperature is one of the reasons for reduced rice yield. Heat stress damages the membrane, inactivates enzymes in the chloroplasts and mitochondria, denaturates or degrades proteins, impairs protein and carbohydrate synthesis, productes new proteins, and inhibits carbon metabolism. Thus to meet up the requirement of increasing population, improved varieties of rice with greater heat tolerance are required. The expression analysis of genes responsible for heat stress tolerance may help mitigate this problem.
The current study was planned in order to standardize the methods for protein isolation, starch isolation, ethanol production, to study the waxy nature of varieties and to do the expression analysis of heat shock protein genes in rice. Four rice varieties, i.e., Swarna, MTU 1010, RRF – 127 and IB – 91 were considered for protein and starch isolation. Two methods, namely alkaline and enzymatic methods, were followed for protein isolation. The maximum pure protein isolated under alkaline method was highest for RRF - 127 (57.04 %) brown rice under 0.2% NaOH treatment while the lowest amount of pure protein was isolated under 0.3% NaOH treatment from IB - 91 (31.92 %) white rice. The enzymatic method gave the highest percentage of
protein isolated from RRF - 127 (61.627 %) and lowest percentage from under the 0.2% NaOH treatment where the lowest extractions were from IB - 91 (40.80 %) white rice under 0.3% NaOH treatment. However, considering both the methods and the two different types of solutions used (0.2% NaOH and 0.3% NaOH), the variety from which the maximum protein could be isolated is RRF – 127 while the variety from which the minimum protein could be isolated is IB – 91. The enzymatic method of protein isolation with 0.2% NaOH treatment is the best method for protein isolation and more protein can be isolated from brown rice as compared to white rice.
Highest starch was isolated from Swarna, followed by IB - 91. The least starch was isolated from RRF – 127. Highest starch was isolated from Swarna, followed by IB - 91. The least starch was isolated from RRF – 127. While estimating in the terms of percentage, taking equal amount of brown rice and white rice, white rice has greater starch percentage in comparison to brown rice. This is because white rice has less of protein, lipids, etc than the brown rice. The RM 263 marker is not linked to the waxy gene of the rice as it does not give correlated results with the amylose content of 18 rice varieties taken for the experimentation. Three varieties, namely Swarna, RRF
– 127 and MTU 1010 were considered for the expression analysis using heat shock protein genes in rice. The capability of heat stress tolerance is highest in RRF – 127. Swarna has comparatively less heat tolerance. MTU 1010 has the least capability of tolerating heat stress. Upregulation of heat shock protein genes was observed in heat stress conditions as compared to the control conditions in all the three varieties with both OsHSP 26.7 and OsHSP 18 genes. The maximum upregulation was observed in RRF – 127 with OsHSP 26.7. MTU 1010 showed the least fold increase in upregulation with both the genes.
Improvements in the standardized methods for protein, starch and ethanol can be made to isolate greater percentages of the respective end products. Marker assisted selection of varieties with waxy nature would make the selection process much easier process than before. Thermo-tolerant rice varieties should be developed to combat the problem of global warming which is increasing day by day.
Description
STANDARDIZATION OF ALKALINE AND ENZYMATIC TECHNIQUES FOR PURIFICATION OF PROTEIN ISOLATES AND PR