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Purification and Characterisation of a Fibrinolytic Enzyme 
from Rhizopus microsporus var. tuberosus


Shuli Zhang, Yingdong Wang, Nan Zhang, Zhe Sun, Yan Shi, Xingnan Cao and Haikuan Wang*


Key Laboratory of Industrial Fermentation Microbiology, College of Biotechnology, Tianjin University of Science and Technology, Ministry of Education, Tianjin , PR China



Article history:
Received August 25, 2014
Accepted March 9, 2015



Key words
Rhizopus microsporus var. tuberosus, fibrinolytic enzyme, purification, characterisation


Summary:
Extracellular fibrinolytic enzyme from Rhizopus microsporus var. tuberosus was purified and characterised. The microorganism was isolated in a distillery from daqu, a fermentative agent used in the production of Chinese liquor and vinegar at different temperatures. The fibrinolytic enzyme was partially purified by ammonium sulphate precipitation, dialysis, DEAE Sepharose® Fast Flow ion exchange chromatography and Sephadex G-75 gel filtration chromatography. The molecular mass of the fibrinolytic enzyme was estimated to be 24.5 kDa by SDS-PAGE. The purified enzyme showed optimal activity at pH=7.0 and 37 °C by fibrin plate method. It showed stronger resistance to the inhibition by trypsin and was stable at 37 °C retaining 96.1 % residual activity after 4 h of incubation. The fibrinolytic activity of the enzyme was enhanced by Na+, Ca2+, Mg2+ and Mn2+. Conversely, Zn2+ and Cu2+ partly inhibited enzymatic activity. Using fibrin plate method, we found that the enzyme not only degrades fibrin directly, but also activates plasminogen into plasmin to degrade fibrin. The results indicate that the pure enzyme has a potential in dissolving blood clot, and the possibility for application in the treatment of thrombosis.


 



*Corresponding author:      hkwang@aliyun.com  
                                       
   +86 022 6060 1058
                                       
   +86 022 6060 2298

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Isolation and Characterisation of Bacteriocin 
and Aggregation-Promoting Factor
Production in 
Lactococcus lactis ssp. lactis BGBM50 Strain  


Nemanja Mirkovic1,2, Zorica Radulovic1, Gordana Uzelac2, Jelena Lozo2,3Dragojlo Obradovic1,
Ljubisa Topisirovic2 and Milan Kojic2*



1Faculty of Agriculture, University of Belgrade, RS-11080 Belgrade, Serbia
2Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, RS-11010 Belgrade, Serbia
3Faculty of Biology, University of Belgrade, RS-11000 Belgrade, Serbia



Article history:
Received August 4, 2014
Accepted March 3, 2015



Key words
bacteriocin lactococcin G, aggregation-promoting factor, plasmid curing



Summary:
Lactococcus lactis ssp. lactis BGBM50, a producer of lactococcin G and aggregation-promoting factor, was isolated from selected lactic acid bacteria taken from semi-hard cheese traditionally produced in the village Žanjic, Montenegro. Strain BGBM50 harbours a number of plasmids of different sizes. Plasmid curing experiments showed that genes for bacteriocin production are located on pBM140, a plasmid 140 kb in length. PCR analysis with primers specific for lactococcin Q and G genes gave fragment of the expected size. In addition, after plasmid curing of strain BGBM50, different derivatives with altered phenotypes were obtained, among them BGBM50-34 strain, which retained bacteriocin synthesis but had enhanced aggregation ability.


 

 

 

*Corresponding author:      mkojic@imgge.bg.ac.rsmkojics@eunet.rs  
                                       
   +381 11 3975 960
                                       
   +381 11 3975 808

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Antagonistic Effect of Pseudomonas sp. CMI-1 on Foodborne Pathogenic Listeria
monocytogenes      


Ágnes Belák* and Anna Maráz


Department of Microbiology and Biotechnology, Faculty of Food Science, Corvinus University of Budapest, 
Somlói út 14–16, HU-1118 Budapest, Hungary



Article history:
Received May 20, 2014
Acceptred January 26, 2015




Key words
antagonistic bacteria, Listeria monocytogenes, siderophore, fluorescent Pseudomonas sp.



Summary:
Bacterial isolates derived from food or raw food materials of animal origin were 
screened for potential antagonistic activity against foodborne pathogenic Listeria monocytogenesUsing the agar spot method, ten out of the 94 tested bacteria showed antilisterial activity. All of the antagonistic isolates identified by sequence analysis as strains of the genus Pseudomonas were able to inhibit the growth of all the examined Listeria species including the ruminal pathogenic L. ivanovii and the opportunistic human pathogenic L. innocuaPseudomonas sp. CMI-1 had the highest inhibitory effect on the growth of different Listeria strains. Co-culturing studies revealed that the inhibition of L. monocytogenes could not be achieved efficiently. Although the population of the Pseudomonas sp. CMI-1 strain increased by up to 10 orders of magnitude during 2 days of culturing period at 20 °C in the presence of L. monocytogenes, the cell count of the pathogen also increased by approx. 6 orders of magnitude. At the same time, appropriate inhibition of cell-free supernatants generated from 6-day-old cultures of Pseudomonas sp. CMI-1 was observed. The inhibitory compound of this antagonistic strain is presumably a chromopeptide siderophore, whose activity and production can be affected by iron supplementation, and which had an absorption maximum typical of siderophores of fluorescent Pseudomonas species. Production of the antilisterial substance was influenced by the oxygen concentration, as in static cultures the concentration of the siderophore was higher than in shake flask cultures.






 

*Corresponding author:   email2   agnes.belak@uni-corvinus.hu  
                                       tel3   
+36 1 482 6360
                                       fax2   +36 1 482 6340
 

 



 

 

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The Efficiency of UVC Radiation in the Inactivation of 
Listeria monocytogenes
on Beef-Agar Food Models



Amir M. Hamidi-Oskouei1*, Christian James2 and Stephen James2


1Department of Food Manufacturing and Automation, National Centre for Food Manufacturing, Holbeach
 Campus, University of Lincoln, Holbeach, PE12 7PT, United Kingdom
2Food Refrigeration and Process Engineering Research Centre (FRPERC), Grimsby Institute (GIFHE), 
 Nuns Corner, Grimsby, North East Lincolnshire, DN34 5BQ, United Kingdom



Article history:
Received October 30, 2014
Accepted January 27, 2015



Key words
Listeria monocytogenes, shortwave ultraviolet light (UVC), food model, white light 
interferometer, microbial deactivation, ready-to-eat beef, surface analysis, emerging technology, nonthermal decontamination



Summary:
The aim of this study is to evaluate the effect of meat content and surface smoothness on the deactivation of Listeria monocytogenes in beef-agar food models achieved by shortwave ultraviolet (UVC) light. Food models with various meat contents were made using chopped beef slices and agar solution. Prepared models together with a Listeria selective agar (LSA) plate and a slice of cooked beef were inoculated with L. monocytogenes and then exposed to UVC light. Population of Listeria reduced to below the level of detection on the LSA plates. As the content of beef in the beef-agar models increased, more L. monocytogenes cells survived. Survival was greatest on the treated cooked slice of beef. To better understand the effect of surface irregularities, a white light interferometer was used to analyse the surface smoothness of beef-agar media and LSA plates. No correlation was observed between the surface roughness of seven out of nine types of produced beef-agar media and the degree of inactivation resulting from UVC radiation at the given dose, whereas, less bacterial cells were killed as beef content of the food models increased. The findings of the current study show that the chemical composition of the treated sample also plays an important role in pathogen resistance and survival, meaning that two samples with similar surface irregularities but different chemical composition might produce very different inactivation results when exposed to UVC light.




 




*Corresponding author:      ahamidi@lincoln.ac.uk  
                                       
   +44 1406 493 000
                                       
   +44 1406 493 030

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Influence of Cultivar and Industrial Processing on Polyphenols 
in Concentrated Sour Cherry (Prunus cerasus L.) Juice  


Maja Repajić1, Danijela Bursać Kovačević1, Predrag Putnik1*, Verica Dragović-Uzelac1,
Josipa Kušt1, Zrinka Čošić2 and Branka Levaj1


1Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, HR-10000
 Zagreb, Croatia
2Maraska d.d., Obala kneza Trpimira 7, HR-23000 Zadar, Croatia



Article history:
Received March 3, 2015
Accepted May 21, 2015


Key words
sour cherry, Marasca cv., Oblačinska cv., juice concentrate processing, polyphenolic content, anthocyanins, antioxidant activity


Summary:
The objective of this study is to investigate the infl uence of cultivar and industrial processing on total polyphenols, anthocyanins, hydroxycinnamic acids and antioxidant activity in concentrated sour cherry (Prunus cerasus L., cvs. Marasca and Oblačinska) juices. Samples were collected during four processing steps: from fresh fruit prior to processing, then from pressed, filtered and concentrated juices. The content of total phenols was the same in both cultivars, but antioxidant activity (Oblačinska>Marasca) and total monomeric anthocyanins (Marasca>Oblačinska) differed. All processing steps significantly influenced the content of total phenols, total monomeric anthocyanins and antioxidant activity. In all samples four major anthocyanins were identified by HPLC with UV/VIS PDA detector, listed in the descending order based on their abundance: cyanidin-3-glucosylrutinoside, cyanidin-3-rutinoside, cyanidin-3-sophoroside and cyanidin-3-glucoside. Marasca cv. contained more total anthocyanins, and contents of cyanidin-3-sophoroside and cyanidin-3-glucosylrutinoside. The content of total hydroxycinnamic acids was also higher in Marasca than Oblačinska cv. After processing, the concentration of all identified anthocyanins increased in both cultivars. Majority of the highest values of polyphenols were detected in the juice after pressing. The content of polyphenols and their antioxidant activity were considerably stable during industrial processing to concentrated juice. Although Marasca had higher polyphenolic content than Oblačinska, both cultivars showed promising industrial potential for processing to concentrated juice.


 

 


 


*Corresponding author:   email   pputnik@alumni.uconn.edu
                                         +385 1 460 5036
                                       
   +385 1 460 5072

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