Quantification of morphochemical changes during in situ enzymatic hydrolysis of individual biomass particles based on autofluorescence imaging

Enzymatic hydrolysis of biomass is an established method for producing biofuels. Lignocellulosic biomass such as corn stover is very inhomogeneous material with big variation on conversion rates between individual particles therefore leading to variable recalcitrance results. In this study, we used noninvasive optical microscopy techniques, such as two-photon microscopy and fluorescence lifetime imaging microscopy, to visualize and analyze morphological and chemical changes of individual corn stover particles pretreated with sulfuric acid during hydrolysis. Morphochemical changes were interpreted based on the fluorescence properties of isolated building blocks of plant cell wall, such as cellulose, hemicellulose, and lignin. Enzymatic hydrolysis resulted in particle size reduction, side wall collapse, decrease of second harmonic signal from cellulose, redshifting of autofluorescence emission, and lifetime decrease attributed to the relative increase of lignin. Based on these observations, tracking compositional change after hydrolysis of individual particles was accomplished. The methodologies developed offer a paradigm for imaging and analyzing enzymatic hydrolysis in vitro and in situ, which could be used for screening enzymes cocktails targeting specific recalcitrant structures or investigating locally enzyme anti-inhibitory agents.

Study on decomposition products of norbixin during bleaching with hydrogen peroxide and a peroxidase by means of UPLC-UV and mass spectrometry

The decomposition products of norbixin, a component of the natural colouring agent annatto, have been studied under bleaching conditions in water and in a whey matrix. In water, several unsaturated aldehydes and ketones of carboxylic acids were identified with UPLC-UV/MS and high resolution mass spectrometry techniques. Based on these products a reaction scheme for the decomposition of norbixin is proposed. In whey, the norbixin is also degraded during bleaching, but no decomposition products are detected. Most likely these products react with endogenous compounds from the whey matrix. For one of these compounds, i.e. cysteine, the formation of a reaction product with 3-acetylacrylic acid (decomposition product of norbixin) was shown.