Srećko Matošić

Adhesion and aggregation ability of probiotic strain Lactobacillus acidophilus M92

Aims: To investigate aggregation and adhesiveness of Lactobacillus acidophilus M92 to porcine ileal epithelial cells in vitro, and the influence of cell surface proteins on autoaggregation and adhesiveness of this strain.

The effect of bile salts on survival and morphology of a potential probiotic strain Lactobacillus acidophilus M92

Bile tolerance is an important criterion in the selection of microbial strains for probiotic use. The survival and morphological changes of a potential probiotic strain, Lactobacillus acidophilus M92, in the presence of bile salts were examined. Lactobacillus acidophilus M92 has shown a satisfactory degree of tolerance against oxgall and individual bile salts tested, especially to taurocholate. The higher resistance of L. acidophilus M92 against taurine-conjugated bile salts relative to deconjugated and glycine-conjugated bile salts was attributed to its reaction to the stronger acidity of the former. Furthermore, bile salt hydrolase (BSH) was active when L. acidophilus M92 was grown in the presence of sodium taurocholate. The rate of BSH activity was highest at the exponential growth phase. It was hypothesised that BSH activity may be important for the bile salt resistance of this strain. The colonial and cellular morphology may also be a valuable parameter in the selection of bile salt-resistant Lactobacillus strains for probiotic use. Smooth (S) and rough (R) colonies, appeared in the original L. acidophilus M92 bacterial culture and demonstrated a different degree of bile tolerance. Rough colonies were more sensitive to bile salts than smooth ones. The R colony cells assumed a round form, probably induced by gaps in the cell wall caused by the cytotoxicity of glycodeoxycholate.

Effect of surfactants on the production of ergot-alkaloids by immobilized mycelia of Claviceps paspali

In a semicontinuous process immobilized Claviceps paspali mycelia produced alkaloids over a period of 60 days (six reincubations). By addition of the surfactant Pluronik, a polyethoxypolypropoxy polymer, a considerable increase in alkaloid biosynthesis occurred. The maximum product concentration achieved was 8.35gl-1, and the overall productivity was 5.80 mgl-1 h-1, which is half the productivity of the batch process. Maximum process productivity for a single reincubation (12.3 mg l-1 h-1) was almost equal to the batch process productivity.