Enhancement of alkaline-oxidative delignification of wheat straw by semi-batch operation in a stirred tank reactor.

This paper compares a semi-batch operation and a conventional one of an alkaline oxidative pretreatment of wheat straw carried out in a stirred tank reactor. For the pretreatment, different concentrations of biomass (6% up to 12% w/v) and two different particle sizes (mesh #40-60 and #>60) were experimented. The performance of processes was evaluated through the analysis of lignocellulosic composition of the biomass, and the enzymatic hydrolysis of pretreated biomass using the Cellic® CTec2 enzyme complex by Novozymes®. The process time of semi-batch operation is significantly lower than the batch one and enables a higher load of biomass, showing a delignification yield between 55 and 60%. In the first 5 h of reaction time, the enzymatic hydrolysis experiments reached their maximum yields of 72 and 66% according to reducing sugars conversion when using the mesh #>60 mesh and #40-60, respectively.

Investigation of food waste valorization through sequential lactic acid fermentative production and anaerobic digestion of fermentation residues.

This work concerns the investigation of the sequential production of lactic acid (LA) and biogas from food waste (FW). LA was produced from FW using a Streptococcus sp. strain via simultaneous saccharification and fermentation (SSF) and separate enzymatic hydrolysis and fermentation (SHF). Via SHF a yield of 0.33gLA/gFW (productivity 3.38gLA/L·h) and via SSF 0.29gLA/gFW (productivity 2.08gLA/L·h) was obtained. Fermentation residues and FW underwent anaerobic digestion (3wt% TS). Biogas yields were 0.71, 0.74 and 0.90Nm3/kgVS for FW and residues from SSF and SHF respectively. The innovation of the approach is considering the conversion of FW into two different products through a biorefinery concept, therefore making economically feasible LA production and valorising its fermentative residues. Finally, a mass balance of three different outlines with the aim to assess the amount of LA and biogas that may be generated within different scenarios is presented.