Under the WP1, (Selection of renewable feedstock for ABE fermentation), the following tasks have been performed:
Between two and three pretreatment methods have been proposed by ITACyl for each of the four agro-food wastes. These methods allow equilibrium between maximal sugar release and minimal generation of fermentation inhibitors in the hydrolysates.
Common fermentation inhibitors for the four agro-food wastes have been identified by BIOPOX, TOMSA, ITACyL with GC-MS and an analytical method for inhibitor quantification by HPLC-UV has been developed. Several detoxification methods for the hydrolysates obtained have been compared.
BIOPOX and CNR-IRC have performed activities on enzymatic hydrolysis of agro-food wastes by different enzymes, as well as reactor operation conditions, which are being optimised. In addition, the new cellulosome enzymes obtained in WP2 will be evaluated soon for their ability to hydrolyse agro-food wastes.
Specifically, the hydrolysis of lignocellulosic biomass catalyzed by cellulase cocktails is a heterogeneous process and includes several phenomena: liquid-solid mass transfer, enzymes adsorption on biomass, cellulose and hemicellulose hydrolysis. Process design asks for reliable cellulase kinetic models. Semi-mechanistic models can be used to describe the heterogeneous process. Kinetic characterization of the commercial cellulases cocktail Cellic CTec2 (Novozymes) has been carried out through three semi-mechanistic models in order to provide reliable tools for the further rational design of reactors for enzymatic hydrolysis of lignocellulosic biomass.
In particular, a study related to the kinetic characterization of the enzymatic hydrolysis is needed in order to obtain a useful tool able to maximize the sugar release depending on the composition of the pretreated biomass during enzymatic hydrolysis. Kinetic characterization of the main used commercial cocktail Cellic CTec2 on apple residues pretreated with NaOH, HCl and laccases has been carried out.
Kinetic parameters showed a faster rate of hydrolysis for the samples with the lower lignin content that were obtained after alkaline pretreatment.
Alternative and cheap nutrient sources for solventogenic bacteria are being assessed by BEUTH. The suitability of these nutrients will be validated by fermenting real hydrolysates.