Ecophysiological approaches to enhance production of the anti-cancer drug taxol by paraconiothyrium variabile and epiccocum nigrum and lysozyme by pichia pastoris

Abstract

This study has investigated the interaction of ecophysiological factors such as water activity (aw), temperature, pH and solute types on (a) the production of the anti-cancer drug taxol by the endophytic fungi Parachoniothyrium variabile and Epcoccum nigrum, and (b) the production of human lysozyme by a recombinant strain of the methanogenic yeast Pichia pastoris. Of more than 200 isolates from fresh health twigs of Taxus baccato trees on the Cranfield University Campus, only two strains of endophytic fungal species, P. variabile and E. nigrum, were able to produce taxol. P. variabile could produce 0.53 to 1.75 g/l taxol and E. nigrum could produce up to 1.32 µg/l in a defined M1D liquid medium. Ecological studies showed the profiles for growth and taxol production. The growth rate of P. variabile were generally higher at 0.99 aw and 25  C, but optimal at 0.99-0.98 aw. The average growth rate was faster when sorbitol was used as the aw depressor when compared with glycerol, glucose and salt-amended media. Statistical analysis indicated that all the studied stress factors significantly affected radial growth rate of P. variabile on a taxol conducive M1D agar (P<0.05). The optimum pH was 5.0 regardless of the aw x temperature conditions (P<0.05). The combined effects of aw, solute types and temperature on taxol production by P. variabile was determined using a 5x5x3 factorial design. The maximum amount of taxol was 7.11 g/l when cultured with M1D using KCl to modified media to 0.98 aw and 25  C. In contrast, on un- amended M1D medium at 25C yielded about 1.75 g/l of taxol. For E. nigrum, optimal conditions for growth were observed at 0.99-0.98 aw and 20-25  C. Growth on medium imposed with sorbitol was significantly faster (P<0.05). All three stress factors significantly affected radial growth rate of this strain (P<0.05). This strain grew faster at pH 5.0. The attenuation of taxol for this strain was observed during examination of the combined effects on taxol yield. Because of the attenuation and unstable production of taxol by the strain of E. nigrum, it was decided to try and use different elicitors to enhance production of taxol. Cont/d.