Chemo-enzymatic saccharification strategy of microalgae chlorella sorokiniana

Biofuel production using microalgae attracted much attention because it can be cultured using CO2 and sunlight. With high carbohydrate content, microalgae have the potential to be used as a fermentation feedstock for bioethanol production. In present work, chemo-enzymatic saccharification of Chlorella sorokiniana microalgae were investigated. Chemical hydrolysis of the biomass followed by enzymatic hydrolysis and was also evaluated the effect of combining the two enzymes and the sequential addition. The effect of α-amylase concentrations was analyzed in ranged between 50 and 8000 U/g of biomass and for amyloglucosidase between 90 and 600 U/g of biomass. The higher concentrations showed the highest conversion of reducing sugars. The α-amylase concentration 8000 U/g of biomass presented a conversion of 43.06 ± 2.92% (w/w), while amyloglucosidase with 600 U/g of biomass obtained 76.57 ± 6.42% (w/w). The combination of two enzymes simultaneously was more efficient than the sequential addition for low enzyme concentrations (α-amylase 50 U/g and amyloglucosidase 90 U/g) with a total reducing sugar of 22.78 ± 3.06 and 16.92 ± 2.06% (w/w), respectively. On the other hand, using the higher enzymes concentrations, no difference was observed between the two addition strategies, 58.9 ± 3.55 and 57.05 ± 2.33% (w/w) for the sequential and simultaneous, respectively. Both strategies didn’t present advantage, since the amyloglucosidase enzyme alone produced slightly higher results. Even thought, the obtained results showed successfully performed saccharification of microalgal biomass and clearly point to microalgae use for saccharification and subsequent bioethanol production.Part of this work has been supported by European governments (INTERREG VA-POCTEP- 2014-2020; 0055_ALGARED_PLUS_5_E) and the Portuguese Science Foundation (FCT) through the grant UID/MAR/00350/2013 to the CIMA of the University of Algarve.info:eu-repo/semantics/publishedVersio

Alternative chemo-enzymatic hydrolysis strategy applied to different microalgae species for bioethanol production

Microalgae have been considered third generation feedstock for biofuel production based on the expectation that large amounts of algal biomass can be cultivated at an acceptable cost. Transformation of biomass into ethanol requires a saccharification step, where complex carbohydrates are broken down by hydrolysis into sugars that can be fermented to bioethanol. Carbohydrate mobilization is hampered by the recalcitrance of the cell envelope of microalgal cells, because complex structural polysaccharides are difficult to depolymerize and make internal carbohydrate reserves inaccessible to hydrolysis. Saccharification can be accomplished by either acidic hydrolysis, enzymatic treatment or a combination of both. The present work focused on the chemo-enzymatic hydrolysis of lyophilized biomass of different microalgae and subsequent fermentation of hydrolysates with higher reducing sugar content. A chemo-enzymatic hydrolysis strategy was defined, consisting of an acid pretreatment carried out at high pressure and temperature, followed by incubation with Amyloglucosidase and finally by incubation with alpha-Amylase, the opposite order of the conventional use of these enzymes. An increase of reducing sugar yield of about one third was observed, and this strategy was successfully applied to a broad group of microalgae, resulting in maximum release yields of at least 34.0 +/- 1.0 g total reducing sugar/100 g dry biomass. For bioethanol production studies, the microalgae hydrolysates of Chlorella sorokiniana, Tetraselmis sp. (Necton) and Skeletonema sp. were selected according to their high reducing sugar content. High ethanol production was achieved with all hydrolysates, with ethanol yields close to the theoretical maximum and the highest ethanol concentrations so far reported under comparable conditions. Chlorella sorokiniana stood out as the best hydrolysate for ethanol production, with an ethanol yield of 0.464 +/- 0.013 g/g reducing sugar and ethanol productivity of 0.344 +/- 0.020 g/L.h.VA-POCTEP-2014-20200055_ALGARED_PLUS_5_E, UID/00350/2020, 0055 ALGARED + 5 Einfo:eu-repo/semantics/publishedVersio