The potential application of aqueous two-phase systems for in situ recovery of 6-pentyl-proportional to-pyrone produced by Trichoderma harzianum

Commercial production of aroma compounds by de novo microbial biosynthesis has been principally limited by the low productivity so far achieved. Produ ction of 6-pentyl-alpha -pyrone (6PP), a coconut-like aroma compound, by Tr ichoderma harzianum has been limited by the toxic effect that occurs even a t low concentration (< 100 ppm). This work evaluated the feasibility of the use of aqueous-two phase systems (ATPS), as in situ extraction systems, in order to overcome the toxic effects of 6PP and to improve culture producti vity. The partition behaviour of 6-pentyl-alpha -pyrone and Trichoderma har zianum mycelium in polyethylene glycol BEG)-salt and PEG-dextran two-phase systems was investigated and it is reported for the first time. The evaluat ion of system parameters such as PEG molecular mass, concentration of PEG a s well as salt, volume ratio (Vr) and dextran molecular mass, was carried o ut to determine under which conditions the 6PP partitions to the opposite p hase that mycelium does. PEG-dextran systems proved to be unsuitable for th e in situ recovery of 6PP because either 6PP and biomass partitioned to thr same phase or a large extraction phase was required for the process. ATPS extraction comprising Vr = 0.26, PEG 1450 (7.2% w/w) and sulphate (16.6% w/ w) provided the best conditions for the maximum accumulation of the biomass into the bottom phase and concentrated the 6PP in the opposite phase (i.e. 86% of biomass and 56% of 6PP of the total amount loaded from the fermenta tion extract into the ATPS) for ex situ bioseparation. However, this system caused complete inhibition of the growth of the microorganism during the i n situ bioseparation, probably as a consequence of the high ionic strength resulting from the salt concentration. Consequently, two ATPS PEG 8000-sulp hate (12%/7% and 6%/14%) were evaluated and proved to be more suitable in t he potential application for the in situ recovery of 6PP. (C) 2001 Publishe d by Elsevier Science Inc.