Rugulopteryx okamurae: Assessment of its potential as a source of monosaccharides for obtaining bio-products

Abstract

Beach-cast seaweed of the invasive brown macroalga Rugulopteryx okamurae was used in this study as raw material to obtain fermentable sugars, which can be converted into high added-value products. The dietary fibre composition of this macroalgae was determined and compared to other brown and red macroalgae, showing one of the highest proportions of dietary fibre (27.3 %) and cellulose (13.6 %). Therefore, the enzymatic hydrolysis of R. okamurae could lead to obtaining hydrolysates with a high concentration of reducing sugars. The main hydrolysis variables (biomass loading, enzyme dose and stirring rates) and the operation mode (fed-batch versus batch) were evaluated to maximize the sugar concentration. Thus, a maximum total reducing sugar concentration of 13.7 g/L was obtained at the optimum conditions: biomass loading of 10 % (w/v), 50 FPU/g biomass, 250 rpm and operating in batch mode. In addition, a kinetic model has been developed to describe the enzymatic hydrolysis of biomass. The model, unlike first-order kinetics, includes a specific term considering the enzyme diffusion through the solid biomass. The proposed kinetic model leads to better fitting of experimental data than the first-order model, especially for long incubation times.