The generation of fermentation inhibitors during dilute acid hydrolysis of softwood

Metabolic engineering of Saccharomyces cerevisiae for improvement in stresses tolerance

“…During acid hydrolysis of lignocellulosic materials, furfural and HMF are generated by dehydration of pentoses and hexoses, respectively, and both furfural and HMF are representative aldehyde inhibitors. 1,2 Aldehydes are toxic to yeasts in inhibition of cell growth [3][4][5] and production of ethanol. 6 Beside aldehydes inhibitors, yeasts need to overcome various stresses during converting sugars to ethanol, such as acid left from pretreatment, high osmotic pressure of hydrolysates, high ethanol concentrations at the last stage of fermentation, high temperature for accelerating fermentation, and process interruptions.…”

La production de carburants à partir de biomasse lignocellulosique par voie biologique : état de l’art et perspectives

“…Pour ce faire, un bon prétraitement doit exposer la cellulose en éliminant les hémi-celluloses qui lui sont associées ; diminuer la cristallinité de la cellulose et créer des zones amorphes ; éliminer ou modifier les lignines qui entravent l'action des cellulases employées dans l'étape suivante. En même temps, pour qu'un prétraitement soit utile et efficace, il est important d'établir des conditions limitant la formation de produits de dégradation qui peuvent inhiber l'étape de fermentation [9][10][11] et de mettre en oeuvre des technologies qui ne nécessitent pas une étape préalable de broyage. Par ailleurs, le catalyseur utilisé pour le prétraitement doit être de faible coût, ou bien recyclable, et le résultat net du procédé doit être l'augmentation de la valeur des différents composants de la biomasse.…”

Evaluation of microorganisms performance in hemicellulosic hydrolyzate detoxification and sugarcane bagasse lignin removal for ethanol production

“…The inhibitory effect on yeast metabolism has been observed at concentrations above 100 mM of formic acid. However, high levels of ethanol have been obtained in the presence of concentrations below 100 mM (LARSSON et al, 1999;TAHERZADEH;NIKLASSON;LIDÉN, 1997).…”

“…In addition to pentose sugars, the hemicellulosic hydrolyzate also contains small amount of other glucose, weak acids, furanic compounds and phenolic compounds (MARTIN et al, 2007;SUN;CHENG, 2005). Depending on the concentration, weak acids, furanic compounds and phenolic compounds are toxic to fermenting microorganisms, inhibiting their metabolism LARSSON et al, 1999), so that they must be removed from the hemicellulosic hydrolyzate prior the fermentation step. In this case, a detoxification step is essential to overcome the metabolism of sugars by the fermenting microorganism (FONSECA et al, 2011(FONSECA et al, , 2013YU et al, 2011).…”

“…Several physical and physico-chemical methods have been developed and applied to remove these degradation products from the lignocellulosic as reviewed by (MUSSATTO; ROBERTO, 2004). The choice of the method depends on both the type of hemicellulose hydrolyzate and the specie of microorganism used for fermenting the sugars, since each microorganism has a different degree of tolerance to inhibitors (LARSSON et al, 1999). The major drawback of many of detoxification methods is that they generate additional waste.…”