Growth and Antimicrobial Production of Acidophiles/Halophiles Bacteria on Olive Mill Waste Water
Cristina M. SAMPAYO*a, Sandra PEREIRAb, and Cidilia PERESa,b,c
a Microbiology group IBET, Ap 12, 2780 Oeiras Portugal
b INIA Quinta do Marques, 2780 Oeiras Portugal
c ITQB, Ap 12, 2780 Oeiras Portugal
The lactic acid fermentation of green olive table is an economically important industry in Portugal. This fermentation is mainly carried out by Lactobacillus plantatum. The bacterial growth is often affected, limited or inhibited by the composition of brines, i.e., high levels of NaC1 (Garrido et al., 1993), phenolic compounds (Etchells et al, 1996; Ruiz-Barba et al., 1990; Juvens and Henis, 1970; Juven et al., 1968) and low pH and temperature of fermentation. On the other hand, olive mill waste waters (OMWW) are a toxic residue from olive oil production. The polyphenols of OMWW can inhibit the growth of some bacteria and Hep2 human cells (Capasso et al., 1995) while Aspergillus niger can hydrolyse polyphenols and tannins, and is used for the bioconversion of OMWW (Hamdi et al., 1991). The utilization of this product as part of a culture medium for the growth of L. plantarum, may be of interest to several points of view. Firstly, OMWW is a direct source of nutritive and toxic substances present in the pulp of olives. Consequently its utilization permits to study their effects on the growth and the metabolism of L. plantarum. A recent study indicates the possibility of using OMWW as part of a culture medium for the growth of L. plantatum has been tested (Rozes and Peres, 1994). A growth medium constituted by OMWW and some adjuvants such as tryprone and agar were used to the growth of L. plantarum. A liquid/solid system was employed. This biphasic system allows to harvest easily the diffusate medium to study the effect of OMWW on the bacterial growth, the metabolism and the production of an antimicrobial compound. It was verified that this acidophile/halophile bacteria can grow on OMWW but at a lower rate than on MRS broth. On the other hand, the production of antimicrobial compound is higher on OMWW than on MRS broth, comparing with biomass production. The combination of a solid and liquid culture medium, and the possibility to do some variations in the concentrations of the constitutive medium substances, in a way that resembles as close as possible the natural environmental of brines (4-8% NaC1, low pH and high levels of phenols) seems an important advantage to understand the real problems of table olive fermentations and its control. In summary, this bacteria can grow under stress condition (NaC1, pH, low temperature, high concentration of phenols) and always keeping its capacity of production an antimicrobial substance.
