Bacteriocins from lactic acid bacteria have been widely studied in recent years; however, there is a little study for explained their chemical compositions. This study was amid to isolate and identification Lactic Acid Bacteria (LAB) from meat in Jeddah -Saudi Arabia on (MRS) medium. Forty isolates of LAB showed antibacterial activities against indicator bacteria Gram negative bacteria K. pneumonia ATCC700603, E.coli ATCC25422, P.aeruginosa, ATCC27583 and Gram positive bacteria S .aureus ATCC25923. Also antibacterial activities was screened by agar well diffusion method, results showed that ten out of 40 (25%) of the tested isolates have activities against all indicator bacteria. Isolates of LAB with the highest antimicrobial effect were identified on the basis of its genetically sequencing. Results revealed that the M8 isolate have 96% identity with Leuconostoc mesentroides and was the highest bacteriocin producer. So it has been selected for the current investigation. The effect of different factors such as (inoculums concentrations, incubation temperature, incubation period, pH and aeration) on the production was studied. The pointed to the best condition for the bacteriocin production of highest amount of bacteriocin was incubation of static culture at 35°C for 24 hr. and pH 6.2.

Lactic  acid  bacteria  produces  a  variety  of  antibacterial  compounds  such  as  organic  acids,  diacetyl,  hydrogen  peroxide  and bacteriocins  or  bactericidal  proteins  as  byproducts  of  fermentation.  Bacteriocins  are  small  proteins  with  bactericidal  or  bacteriostatic activity  against  genetically  closely  related  species.  Some  bacteriocins  are peptides  consisting  of only  13 to 37 amino  acids.  Some  small bacteriocins  contain  unusual  amino  acids  originating  from  modifications  of  conventional  amino  acids  after  translation.  Bacteriocins  are natural  peptides  secreted  by  several  bacteria  that  exert  bactericidal  activity  against  other  bacterial  species.  Research  in  this  topic is promoted  not only by the need to develop  alternatives  to antibiotics  and drugs  that have shown  non-desirable  effects,  but also to the capacity of some bacteriocins  to inhibit saprophytic  and food-borne  pathogens  in food stuffs. The purification  of bacteriocins  produced is helpful  for  the  knowledge  of  the  mechanism  of  action,  structure,  and  other  characteristics,  which  helps  to  isolate  the  bacteriocin biosynthetic  genes. In this study, purified  bacteriocins  from Leuconostoc  mesenteroides  were described.  The frequently  applied  techniques involve ammonium  sulfate salt precipitation.  The results obtained through the purification  of Leuconostoc  mesentroides  bacteriocins  carried out  its  antimicrobial  activity,  thermostable  and  the  effected  of  pH.  the  incubation  of  temperature  on  bacteriocin  activity  in  terms  of inhibition zones. The data recorded that the bacteriocin was active in a wide range of pH, the maximum activity was observed at pH 6.0 to 7.0, but at high pH of 8.0 the activity of the bacteriocin gradually decreased. Bacteriocin could retain its antimicrobial  activity partially when there was a shift to acidic or basic range. It has been found to be thermo  stable in nature  as it can withstand  high temperatures  up to 121°C,  although  a partial  loss in the activity  was  observed  with  a continuous  increase  in temperature.  Bacteriocins  carried  out for its antimicrobial  activity, thermostable  and the effect of pH.