Due to problem of preservation of dairy products which serve as a matrix for probiotics, it is challenging to use these probiotics as food supplements in many developing countries. To determine the suitability of the Lactobacillus strains for exploitation as probiotics in honey, we investigated the effect of their storage on the viability, functionality, and the mechanism associated with their protective effect. Three isolates obtained from our laboratory collection were identified through amplification of the 16S rRNA gene. The viability of the strains in honey at different storage conditions was studied. Three genes (hdc, gtf, and clpL) responsible for the resistance of bacteria in acidic environments were screened. SDS-PAGE analysis of total protein was performed to observe protein profile changes of the strains after exposure to honey. All the three isolates, namely, GGU, GLA51, and GLP56, were identified as Lactobacillus plantarum strains. After 28 days of storage in honey at 4 °C, viable cell concentrations of the three strains were higher than 2.04 × 10 CFU/ml. During the same period at room temperature, only the Lactobacillus plantarum GLP56 strain remained viable with a cell concentration of 1.86 × 10 CFU/ml. The clpL gene coding for ATPase was detected in all the three strains. The protein of molecular weight ~ 50 kDa was absent in the protein profile of Lactobacillus plantarum GGU after 60 days of storage in honey at 4 °C. The Lactobacillus plantarum GLP56, Lactobacillus plantarum GLA51, and Lactobacillus plantarum GGU strains exposed to honey can withstand acidic environmental stress but their viability declines over time.

Abstract:The present investigation reports the characterization of the bacteriocin produced by the probiotic strain Lactobacillus plantarum 29V isolated from raw cow milk in the Western's highlands of Cameroon, as well as the viability of this strain in the palm kernel oil. The antimicrobial compound synthesized by Lactobacillus plantarum 29V was sensitive to some proteolytic enzymes. It showed remarkable stability at high temperatures and in the presence of organic solvents, detergents and surfactants. It was also active in pH 2.0-10 and NaCl range of 1-7%. The neutralized cell-free supernatant of this bacterium inhibited the growth of several Lactobacillus spp., pathogenic and food spoilage microorganisms. The results of this study showed that palm kernel oil maintains the viable cell numbers of the probiotic strain Lactobacillus plantarum 29V, without any changes of peroxide and acid indexes of palm kernel oil.

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The contribution of selected ropy and capsular Lactobacillus plantarum 162RM on texture of fermented milk as well as on the functionality of kareish cheese was established in this study. The cell suspension of this strain was used in combination with commercial starter cultures MY900 (Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus) and MM100 (Lactococcus lactis ssp. lactis, Lactococcus lactis ssp. cremoris and Lactococcus lactis ssp. diacetyllactis) obtained from Rhodia Food to manufacture fermented milk and Kareish cheese respectively. The final pH of fermented milks manufactured with the combination of starter MY900 and different concentration of strain L. plantarum 162RM were not significantly different. Fermented milk hardness, consistency, and adhesiveness increased significantly when 8 % (V/V) of strain Lactobacillus plantarum 162RM was used. This strain produces exopolysaccharides (EPS), which by attaching to the casein matrix increases and improves the texture characteristics of fermented milk. The Experimental Kareish Cheese (EKC), made by pairing commercial starter MM100 with 8% (v/v) of L. plantarum 162RM were also compared to Control Kareich Cheese (CKC) in terms of their moisture content and textural properties. The EKC showed the greatest moisture retention and the use of ropy and capsular strain of L. plantarum 162RM affects significantly some textural properties of EKC cheese, relative to the control. The CKC samples were gummier and more chewy than the EKC fresh samples. It is therefore evident that, used in appropriate amount, this strain can increase moisture content in low fat Kareish cheese leading to improvement of textural properties.

Lactobacillus plantarum Lp6SH isolated from "Sha'a" a maize-based traditionally fermented beverage from Cameroon, produces a bacteriocin active against Gram-positive and Gram-negative bacteria including Listeria innocua, Staphylococcus aureus, Salmonella typhi, Bacillus cereus, Streptococcus mutans, Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumonia and Shigella flexneri. Highest bacteriocin production in buffered MRS broth medium was achieved after 6 h of incubation without agitation. The bacteriocin is of proteinaceous nature as judged by the complete loss of activity after treatment by proteolytic enzymes. Interestingly, this bacteriocin was stable at 121°C for 30 min, over a wide range of pH (2.0-10.0), and when treated with surfactants, organic solvents, EDTA and NaCl. The activity remained after 8 months of storage at 4°C and the mode of action against Salmonella typhi ATCC 6539 was bactericidal. The bacteriocin was partially www.ccsenet.org/ijb International Journal of Biology Vol. 4, No. 2; April 2012 ISSN 1916-9671 E-ISSN 1916 150 purified using ammonium sulphate precipitation, gel filtration and cation exchange chromatographies. Mass Spectrometry Analysis showed that the Molecular weight of the bacteriocin is 2.340 kDa.