Diversity and osmoregulatory responses of bacteria isolated from two-phase olive oil extraction waste products

Six phenotypically distinct groups of bacteria were isolated from Spanish and Greek sources of alpeorujo, the waste from two-phase decanter, continuous extraction olive oil mills. These different bacteria isolated from alpeorujo showed different growth and osmoregulatory responses to conditions of reduced water activity (a(w)), and there was a correlation between the ability of isolates to withstand low a(w) and grow on alpeorujo. One isolate (1A), which grew particularly well both on alpeorujo and in nutrient broth containing either 10% NaCl or 30% sucrose, was identified as being most closely related to Bacillus amyloliquifaciens using biochemical tests and partial 16S rDNA gene sequence analysis. Bacillus sp. strain 1A was found to display an atypical membrane lipid response at low a(w) since the major change was an increase in the zwitterionic phosphatidylethanolamine rather than an anionic phospholipid such as phosphatidylglycerol. In addition, instead of the expected decrease, there was an increase in the average lipid fatty acid acyl chain length at low a(w) without any other compensatory fluidizing change.