BIOSURFACTANTS FROM THERMOPHILIC DAIRY STREPTOCOCCI AND THEIR POTENTIAL ROLE IN THE FOULING CONTROL OF HEAT-EXCHANGER PLATES

Recent work on biosurfactant release by thermophilic dairy streptococc i is reviewed, There is a suggestion that Streptococcus thermophilus i solates may release biosurfactants that stimulate detachment of alread y-adhering cells and leave an anti-adhesive coating on a substratum. A previously published rapid screening method is described for the iden tification of biosurfactant-releasing microorganisms, and growth mediu m supplements to enhance biosurfactant release by thermophilic dairy s treptococci are reported, New experimental work described includes the isolation and purification of biosurfactants from dairy isolates by t hin layer chromatography, Many compounds isolated were extremely surfa ce-active and reduced the water surface tension to values around 30 mJ m(-2) at a concentration of 10 mg ml(-1). Most importantly, the thin layer chromatograms of various isolates resembled each other, and an a dsorbed purified compound from one isolate retarded the deposition to glass of another isolate by a factor of two, Provided our findings imp licate that these biosurfactants could also be adsorbed to heat exchan ger plates in pasteurizers and thereby retard colonization by thermoph ilic streptococci, these compounds may have major economic implication s, Further work is required, however.