Sandrasegarampillai Balakumar

Isolation and improvement of a thermotolerant Saccharomyces cerevisiae strain

The ambient temperature is a drawback in industrial ethanol production in Jaffna due to heat killing of yeast during fermentation. Thus a search was initiated for thermotolerant organisms suitable for fermentation in hot climates. The screening of the best wild-type organisms was undertaken as the first step. Thermotolerant strains were selected from environments where there are chances of organisms being exposed to high temperature. The samples were enriched and screened for thermotolerant organisms which survived at 45 °C for 15 h. Among the yeast strains selected from different sources, thermotolerant strains with the capacity to withstand 45 °C for 15 h were found in samples collected from the compost heap and distillery environments. Three colonies from the distillery environment were selected for further studies and named p1, p2 and p3. Exponential phase (18 h) cultures of p1, p2 and p3 were subjected to 15 temperature treatment cycles (at 50 °C each for 3 h) and thermally adapted strains pt1, pt2 and pt3 were obtained, showing 100, 30 and 20% viability at 50 °C for 30 min respectively. The initial round of thermal adaptation cycles increased the duration of 100% viability from 20 h (p1) to 68 h (pt1) when incubated at 40 °C. Very little benefit was obtained when pt1 was treated with u.v. and ethyl methanesulphonate. The selected strain was identified and designated as Saccharomyces cerevisiae S1. The ethanol produced from 100 g glucose l−1 by S. cerevisiae S1 was 46 g l−1 (36 h), 38 g l−1 (48 h) and 26 g l−1 (48 h) at 40, 43 and 45 °C respectively in rich nutrient medium.

Biochemical changes associated with germinating rice grains and germination improvement.

Abstract To determine biochemical changes during the germination of rice grains ( Oryza sativa L. subsp. indica var. Mottaikaruppan) and to improve germination rate using gibberellic acid and surfactants [sodium dodecyl sulfate (SDS) (1.0 g/L) and Triton-X−100 (1.0 mL/L)], whole rice grains soaked in distilled water for 12 h at 30°C were germinated in the dark at 30°C for five days. The highest germination rate (77.1%) was obtained on the 5 th day. An increase in the content of reducing sugars from 7.3 to 58.1 mg/g DM (dry matter) was observed from the 1 st day of germination. Free amino acids and soluble protein contents increased to 3.69 and 5.29 mg/g DM, respectively on the 5 th day of germination. Total protein content decreased from 100.5 to 91.0 g/kg DM during germination. Increases in amylolytic (1.1 to 190.0 U/g DM) and proteolytic (0 to 0.12 U/g DM) activities were observed during germination. Effects of different concentrations of gibberellic acid on the germination of rice grains were evaluated and 0.1 g/L was found to promote germination. When effects of gibberellic acid (0.1 g/L) and surfactants were evaluated individually and together, higher germination rate was observed in the control experiment (grains germinated in distilled water), whereas giberellic acid and surfactants decreased the germination rate. Therefore, the flour obtained from the grains germinated for four days using distilled water to obtain high content of soluble materials and enzyme activities can be used in preparation of bakery items.

Optimization of Bread Preparation from Wheat Flour and Malted Rice Flour

Abstract The feasibility of partially replacing wheat flour with malted rice flour in bread making was evaluated in several formulations, aiming to find a formulation for the production of malted rice-wheat bread with better nutritional quality and consumer acceptance. The whole grains of a local rice variety ( Oryza sativa L. subsp. indica var. Mottaikaruppan ) were steeped in distilled water (12 h, 30°C) and germinated for 3 days to obtain high content of soluble materials and amylase activity in bread making. The quality of bread was evaluated by considering the physical and sensorial parameters. When the wheat flour was substituted with malted rice flour, 35% substitution level and the malted rice flour from 3 days of germination was the best according to the physical and sensory qualities of bread. The quality of bread was improved by the addition of 20 g of margarine, 20 g of baking powder and 20 g of yeast in 1 kg of flour. Among different ratios of yeast and baking powder, 2:1 was the best. Bread improver containing amylases and oxidizing agents at the concentration of 40 g/kg was selected as the best concentration. When comparing the final formulation made in the bakery with wheat bread, malted rice-wheat bread contains more soluble dietary fiber (0.62%), insoluble dietary fiber (3.95%), total dietary fiber (4.57%) and free amino acid content (0.64 g/kg) than those in wheat bread (0.5%, 2.73%, 3.23% and 0.36 g/kg, respectively).

Physical, chemical and microbial analysis of bottled drinking water

INTRODUCTION People rely on the quality of the bottled drinking water, expecting it to be free of microbial contamination and health hazards. OBJECTIVES To evaluate the quality of bottled drinking water sold in Jaffna peninsula by analysing the physical, chemical and microbial contents and comparing with the recommended Sri Lankan Standard (SLS) values. METHODS All bottled water samples sold in Jaffna peninsula were collected. Electrical conductivity, total dissolved solid, pH, calcium, nitrate, total aerobic and anaerobic count, coliform bacterial count and faecal contamination were checked. RESULTS These are 22 brands of bottled drinking water sold in Jaffna peninsula. The sample had very low electrical conductivity when compared with SLS (750 μS/ cm) and varied from 19 to 253 μS/cm with the mean of 80.53 (±60.92) μS/cm. The pH values of the bottled drinking water brands varied from 4.11 to 7.58 with a mean of 6.2 (±0.75). The total dissolved solid content of the bottled drinking water brands varied from 9 to 123.67 mg/l with a mean of 39.5 (±30.23) mg/l. The calcium content of the bottled drinking water brands varied from 6.48 to 83.77 mg/l with a mean of 49.9 (±25.09) mg/l. The nitrate content of the bottled drinking water brands varied from 0.21 to 4.19 mg/l with the mean of 1.26 (±1.08) mg/l. Aerobic bacterial count varied from 0 to 800 colony forming unit per ml (cfu/ml) with a mean of 262.6 (±327.50) cfu/ml. Among the 22 drinking bottled water brands 14 and 9% of bottled drinking water brands showed fungal and coliform bacterial contaminants respectively. The water brands which contained faecal contamination had either Escherichia coli or Klebsiella spp. CONCLUSIONS The bottled drinking water available for sale do not meet the standards stipulated by SLS.

Prevalence and risk factors of diabetes mellitus among adults in Jaffna District

A cross sectional descriptive study was carried out to determine the prevalence and risk factors of diabetes mellitus among adults in Jaffna District. Multistage stratified cluster sampling technique was employed to select 544 participants. An interviewer administrated questionnaire was used. Anthropometric and blood pressure (BP) measurements were recorded and biochemical parameters were analysed. Response rate was 95.3%. Of them, 224 (43.8%) were male. The prevalence of diabetes mellitus was 16.4% (95% CI: 13.3- 19.9); in males 19.6% (95% CI: 14.6-25.4) and in females 13.9% (95% CI: 10.1-18.5). Of the diabetics, 27.4% were previously undiagnosed. In the final multivariable model, participants with family history of diabetes were 3.5 times (p<0.001) more likely and those with high waist hip ratio were 2 times (p=0.009) more likely to develop diabetes mellitus.