Influence of di-rhamnolipids on the enzymatic hydrolysis of steam-pretreated eucalyptus wastes

In this present work, rhamnolipids produced from Pseudomonas aeruginosa TGC07 were evaluated as bio-surfactants for enzymatic hydrolysis of steam pretreated (not delignified) eucalyptus wastes comparatively to the synthetic surfactant Triton X-100. Enzymatic hydrolyses were performed at different substrate loadings (1%, 5% or 10% w/w) using commercial enzymes (Cellic (R) CTec1) at different dosages (14 or 28 FPU/g(cellulose)). The di-rhamnolipids were characterized by NMR spectroscopy. Cellulose conversions higher than 60% were achieved after 72 h runtime with the use of di-rhamnolipids at 5% solids, i.e., significantly superior to the conversions obtained from experiments performed without use of any surfactant, and similar to the performance of synthetic Triton X-100 at 5% solids. These results evidence that the use of natural renewable di-rhamnolipids as bio-surfactants emerges as an interesting environmentally-friendly alternative to replace synthetic surfactant Triton X-100 as surfactant, aiming to increase production yields of cellulosic sugars by enhancing enzymatic hydrolysis of lignocellulosic biomasses such as steam pretreated eucalyptus wastes.