Wheat straw lignin degradation induction to aromatics by por Aspergillus spp. and Penicillium chrysogenum

Wheat straw is a recalcitrant agricultural waste; incineration of this material represents an important environmental impact. Different reports have been made regarding the use of the structural components of wheat straw, i.e. cellulose, hemicellulose and lignin; however, lignin has been less exploited because it is largely considered the recalcitrant part. Residual wheat straw lignin (REWSLI) has a potential biotech-nological value if depolymerization is attained to produce aromatics. Ligninolytic mitosporic fungus represent an alternative where very little research has been done, even though they are capable of depol-ymerize REWSLI in simple nutritional conditions in relatively short periods, when compared to basidio-mycetes. The aim of this research was to study the depolymerization activity of Aspergillus spp and Penicillium spp on semipurified REWSLI as the sole carbon source to produce aromatics. The depoly-merization capacity was determined by the activity of the laccase, lignin peroxidase and manganese peroxidase enzymes. The generated aromatics derived from the REWSLI depolymerization were identi-fied by gas chromatography. Obtained results revealed that Penicillium chrysogenum depolymerized the lignin material by 34.8% during the 28-day experimentation period. Laccase activity showed the largest activity with 111 U L-1 in a seven-day period, this enzyme induction was detected in a smaller period than that required by basidiomycetes to induce it. Moreover, the enzymatic activity was produced with-out the addition of an extra carbon source as metabolic inductor. Aspergillus spp and Penicillium spp generated guaiacol, vanillin, and hydroxybenzoic, vanillinic, syringic and ferulic acid with a maximum weekly production of 3.5, 3.3, 3.2, 3.3, 10.1 and 21.9 mg mL-1, respectively.