Stimulation of novel thermostable extracellular lipolytic enzyme in cultures of Thermus sp.

Abstract

Selected organisms from the genus Thermus ( T. aquaticus YT1, T. thermophilus HB8 and HB27) offer new opportunities for biocatalysis and biotransformations as a result of the extreme stability of their enzymes. In order to favour the secretion of extracellular lipolytic enzymes the effect of temperature and carbon source has been studied. All strains were able to grow within a wide temperature range (from 60 to 80 °C) with an optimum value of 70 °C for extracellular lipolytic activity. On the other hand, several sugars were used as carbon source in the culture medium at different concentrations (from 0.5 to 14 g dm −3). Supplementation of monosaccharides (glucose, fructose) and disaccharides (maltose, sucrose) was carried out in an attempt to increase biomass and lipolytic enzyme production. The influence of carbon source was variable, depending on the strain. Nevertheless, the addition of low concentrations of mono- or disaccharides helped to improve the productivity of the process in most cases. The most significant effects on extracellular lipolytic activity were detected in T. thermophilus HB27 and T. aquaticus YT1 cultures, using sucrose and fructose as carbon source at an initial concentration of 0.5 g dm −3. Moreover, the effect of addition of lipids (olive oil, coconut oil and tributyrin) was tested. In T. thermophilus HB27 cultures, the highest extracellular lipolytic activities were obtained when olive oil was added (70% higher than those obtained in control cultures).