The intracellular aminopeptidase activities and volatile compound profile of isolated halophilic lactic acid bacteria Tetragenococcus halophilus was investigated. Tetragenococcus halophilus CH2-4 and CH6-2 exhibited highest aminopeptidase activities 2.2 U/mL toward Glutamic-pNA. Meanwhile T. halophilus CH6-1 and V7-2 showed highest aminopeptidase activities 1.4 U/mL toward Leucine-pNA. The total 19 volatile compounds, including esters, alcohols, ketones, phenols, hydrocarbons and sulfur containing compounds were detected in fish broth inoculated with T. halophilus.T. halophilus CH6-2 produced most volatile compounds, 10/19 detected ones in this study.
In this study, several factors affecting Tetragenococcus halophilus CH6-2 cell survival rate in spray drying process including growth conditions, protective agents, and stress adaption were investigated. T. halophilus CH6-2, which was grown in different media, was mixed with different protective agents or at different ratios of cell concentration to protective agents or was subjected to stress adaption before spray drying. The survival rate after spray drying and after storage was determined. The results showed that skim milk had the strongest protective effect on T. halophilus CH6-2 cells during spray drying. De Man, Rogosa and Sharpe (MRS) was a better medium than our developed M7 optimal medium for culturing T. halophilus CH6-2 in respect of survivability after storage. Increasing the cell/protective agent ratio from 1/20 to 1/3 could increase the survivability after spray drying but not during storage. The heat stress and osmotic stress in this study did not improve the cell survivability after spray drying and storage.
The effects of different physical and technological parameter such as time, substrate to liquid ratio, enzyme concentration, temperature, and pH on enzymatic saccharification of alkaline pretreated straw cellulose were studied. For alkaline pretreatment, the straw was incubated with 10 % NaOH at ratio 1:20 (w/v) at 90 °C for 1 hour. After the alkaline pretreatment the cellulose content increased from 50.2 % (w/w) to 67.3 % (w/w). Enzyme used for saccharification of treated and untreated straw was produced from Cellulosimicrobium sp MP1 which was isolated from termite gut. Results from research showed that the highest percentage of saccharification of alkaline pretreated straw was 69.91 %, corresponding to 10.58 mg/mL of reducing sugar. The hydrolysis conditions for reaching this highest saccharification yield were: temperature of 55 ºC, substrate to liquid ratio of 2 g/100 mL, enzyme concentration of 37.5 U/g, pH of 5.5 and hydrolysis time of 48 hours.
In this study, factors affecting the extraction yield of carotenoids from dry shrimp waste by organic solvents such as ratio of hexane / acetone, ratio of solvent / shrimp waste, extraction temperature, extraction time, extraction method such as dynamic or static have been studied. The results showed that the solvent ratio hexane: acetone = 3: 1 gave the highest carotenoid yield. In this ratio of solvent’s mixture, the yield reached highest at temperature 60 °C for 2 hours, which was 44,64 µg / g raw shrimp waste (d.b.) (ratio of solvent to raw material 3/1). Ultrasound or vortexing gave higher extraction yield than in static conditions, which was 1.5- to 1.8- fold increase, respectively. At the ratio of solvent: dried shrimp = 4: 1, the amount of carotenoid recovered at 60°C for 2 hours reached 57.4 µg / g. However, if the shrimp waste was hydrolyzed with Alcalase at 50°C for 4 hours before extraction by solvent, the amount of carotenoid recovered achieved 149 µg / g of raw material
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