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

摘要

Commercial production of aroma compounds by de novo microbial biosynthesis has been principally limited by the low productivity so far achieved. Production of 6-pentyl-a-pyrone (6PP), a coconut-like aroma compound, by Trichoderma harzianum has been limited by the toxic effect that occurs even at 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 productivity. The partition behaviour of 6-pentyl-a-pyrone and Trichoderma harzianum mycelium in polyethylene glycol (PEG)-salt and PEG-dextran two-phase systems was investigated and it is reported for the first time. The evaluation of system parameters such as PEG molecular mass, concentration of PEG as well as salt, volume ratio (Vr) and dextran molecular mass, was carried out to determine under which conditions the 6PP partitions to the opposite phase that mycelium does. PEG-dextran systems proved to be unsuitable for the in situ recovery of 6PP because either 6PP and biomass partitioned to the 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 fermentation extract into the ATPS) for ex situ bioseparation. However, this system caused complete inhibition of the arowth of the microorganism during the in situ bioseparation. probably as a consequence of the high ionic strength resulting from the salt concentration. Consequently, two ATPS PEG 8000-sulphate (1 2%/7% and 6%114%) were evaluated and proved to be more suitable in the potential application for the in situ recovery of 6PP.