Increase in 6-pentyl-alpha-pyrone production by Trichoderma spp. in liquid medium using in situ removal by adsorbent...

The Trichoderma-produced secondary metabolite 6-pentyl-alpha-pyrone (6-PP) has demonstrated promise for agricultural applications, but cost-effective bioproduction remains limited by product inhibition during fermentation. This study aimed to evaluate the effect of media type on 6-PP production in T. atroviride IMI206040, screen production by nine New Zealand Trichoderma strains, and assess Amberlite XAD-4 in situ product removal in five strains to overcome self-inhibition. T. atroviride IMI206040 was cultured for 5 days in potato dextrose broth (PDB) or minimal media supplemented with ammonium or nitrate, and 6-PP production was assessed by thin-layer chromatography (TLC). The ten Trichoderma strains were cultured for 7 days in PDB and 6-PP production quantified by spectrophotometry. Finally, five strains were cultured in PDB for 14 days with and without Amberlite XAD-4, and 6-PP quantified by spectrophotometry and gas chromatography (GC). In T. atroviride IMI206040, PDB supported the highest 6-PP production, while ammonium-based minimal media repressed production, consistent with nitrogen catabolite repression. Screening revealed up to 14.6-fold variation among strains, with T. gamsii LU771 and T. viridescens LU1369 as the highest producers. Spectrophotometric and GC measurements showed strain-dependent disagreement, indicating GC is more reliable for cross-strain comparisons. Amberlite XAD-4 increased total 6-PP production 3- to 5.2-fold across all five strains, with > 99% of secreted 6-PP sequestered. The highest-producing strains, T. gamsii LU771 and T. atroviride LU132, achieved titres approaching 500 mg/L. These findings support Amberlite XAD-4 as an effective in situ product removal method for increasing 6-PP bioproduction and identifying strains with high intrinsic biosynthetic capacity in the absence of product inhibition.