scholarly journals A mild pulsed electric field condition that improves acid tolerance, growth, and protease activity of Lactobacillus acidophilus LA-K and Lactobacillus delbrueckii subspecies bulgaricus LB-12

2013 ◽  
Vol 96 (6) ◽  
pp. 3424-3434 ◽  
Author(s):  
N. Najim ◽  
Kayanush J. Aryana
Keyword(s):  
Electric Field ◽  
Field Condition ◽  
Lactobacillus Acidophilus ◽  
Protease Activity ◽  
Acid Tolerance ◽  
Pulsed Electric Field ◽  
Lactobacillus Delbrueckii

scholarly journals The effect of mild Pulsed Electric Field (PEF) conditions on acid tolerance, bile tolerance, growth and protease activity of the Lactobacillus delbrueckii ssp. bulgaricus LB-12.

2011 ◽  
Vol 35 (1) ◽  
pp. 60-70
Author(s):  
Najim Hadi Najim
Keyword(s):  
Electric Field ◽  
Protease Activity ◽  
Mixed Model ◽  
Acid Tolerance ◽  
Pulsed Electric Field ◽  
Repeated Measurements ◽  
Lactobacillus Delbrueckii ◽  
Logarithmic Phase ◽  
Bile Tolerance ◽  
Mrs Broth

Pulsed electric field (PEF) processing involves the application of pulses of voltage for less than one second to fluid products placed between two electrodes. So this study was conducted for the quantitative assessments of mild PEF conditions on acid tolerance, growth, bile tolerance and protease activity of Lactobacillus delbrueckii ssp. bulgaricus LB-12. The control and PEF treated samples were prepared by inoculating 10 ml of freshly thawed culture of Lactobacillus delbrueckii ssp. bulgaricus LB-12 into 990 ml of sterile 0.1% (wt/v) peptone water and treated in a pilot plant PEF system (OSU-4M). The treatments were positive square unipolar pulse width of 3 μs, pulse period of 0.5 second, voltage of 1 kV/cm, delay time of 20 μs and flow rate of 60 ml/min at 40.5°C. The control was passed through the PEF system (60 ml/min) without receiving any pulsed electric field condition. The acid tolerance was determined every 30 minutes for 120 minutes of incubation in acidified MRS broth at pH 2. Growth was determined hourly for 25 hours of incubation at 37°C in MRS broth. The bile tolerance was determined hourly for 16 hours of incubation in MRS-Thio broth . Samples were plated in duplicates using pH modified Lactobacilli MRS agar. The petriplates were incubated anaerobically at 43C for 72 hours. Protease activity was determined by o-phthaldialdehyde (OPA) UV- spectrophotometric assay at 0, 12, 24, 36 and 48 hours of incubation of conducted. inoculated skim milk at 40°C. Three replications were The control. The stationary phase of the bacterium was between hours 10 and 18. Moreover significant experimental design was repeated measurements on complete randomized block, Replications were the blocks. Data were analyzed using Proc Mixed model of Statistical Analysis System (SAS).The viability of the control Lactobacillus delbrueckii ssp. bulgaricus LB-12 was lost after 30 minutes of incubation in acidified MRS broth (pH 2), whereas, the bacterium subjected to mild PEF treatment was acid tolerant until the end of 120 minutes of incubation. Mild PEF significantly improved acid tolerance of Lactobacillus delbrueckii ssp. bulgaricus LB-12. and the growth reached the logarithmic phase an hour earlier than the decrease 

scholarly journals The Influence of Mild Pulsed Electric Field (PEF) on Acid Tolerance, Bile Tolerance, Growth and Protease Activity of the Dairy Culture Bacteria Lactobacillus acidophilus LA-K

2013 ◽  
Vol 37 (1) ◽  
pp. 775-82
Author(s):  
Najim H. Najim
Keyword(s):  
Electric Field ◽  
Flow Rate ◽  
Lactobacillus Acidophilus ◽  
Protease Activity ◽  
Acid Tolerance ◽  
Pulsed Electric Field ◽  
Growth Patterns ◽  
Logarithmic Phase ◽  
Bile Tolerance ◽  
Mrs Broth

The objective of this study was to determine the influence of mild PEF conditions on acid tolerance, growth, bile tolerance and protease activity of L. acidophilus LA-K. The treatments were positive square unipolar pulse width of 3 µs, pulse period of 0.5 second, voltage of 1 kV/cm, delay time of 20 µs and flow rate of 60 ml/min at 40.5°C PEF treatment temperature. The control was passed through the PEF system at the same flow rate (60 ml/min) without receiving any pulsed electric field condition. The acid tolerance was determined every 30 minutes for 120 minutes of incubation in acidified MRS broth at pH 2. Growth of the culture was determined hourly for 32 hours of incubation at 37°C in MRS broth. The bile tolerance was determined hourly for 16 hours of incubation in MRS-Thio broth supplemented with 0.3% (w/v) Oxgall (bovine bile) and 0.2% sodium thioglycolate. Samples were plated in duplicates using Lactobacilli MRS agar. The petriplates were incubated anaerobically at 37C for 48 hours. Protease activity was determined by o-phthaldialdehyde (OPA) spectrophotometric assay at 0, 12, 24, 36 and 48 hours of incubation of inoculated skim milk at 40°C three replications were conducted. The experimental design was repeated measurements on complete randomized block, replications were the blocks. Lactobacillus acidophilus subjected to mild PEF conditions as well as the control were acid tolerant until the end of the 120 minutes of incubation but there was a significant (P<0.0001) decrease in the viable bacterial counts after each incubation time of 30 minutes. Mild PEF conditions studied significantly improved acid tolerance of the bacterium. The mild PEF treated culture reached the logarithmic phase of the growth an hour earlier than the control. Lactobacillus acidophilus LA-K exhibited tolerance to the bile conditions and exhibited similar growth patterns in the presence or absence of bile acids but the bacterium reached the stationary phase after 12 hours of incubation in bile conditions compared to 16 hours of incubation in the absence of bile conditions. Mild Pulsed Electric Field conditions had insignificant effect on bile tolerance of L. acidophilus LA-K. Mild Pulsed Electric Field treatment significantly (P<0.0001) enhanced the protease activity of the bacterium compared to the control.

Influence of Pulse Width on Polyphenol Extraction from Agricultural Products by Pulsed Electric Field

2013 ◽  
Vol 133 (2) ◽  
pp. 32-37 ◽  
Author(s):  
Akira Nakagawa ◽  
Hitoshi Hatayama ◽  
Koichi Takaki ◽  
Shoji Koide ◽  
Yukio Kawamura
Keyword(s):  
Electric Field ◽  
Pulse Width ◽  
Pulsed Electric Field ◽  
Agricultural Products ◽  
Polyphenol Extraction
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