Kinetics of the hydrolysis of polysaccharide galacturonic acid and neutral sugars chains from flaxseed mucilage

Different hydrolysis procedures of flaxseed polysaccharides (chemical and enzymatic) were carried out with H2SO4, HCl and TFA at different acid concentrations (0.2, 1 and 2 M) and temperatures (80 and 100°C). Enzymatic and combined chemical and enzymatic hydrolyses of polysaccharide from flaxseed mucilage were also studied. Acid hydrolysis conditions (2 M H2SO4, 4 h, 100°C) are required to quantify total monosaccharide content of flaxseed mucilage. The enzymatic pathway (Pectinex™ Ultra SP) limits sugar destruction during hydrolysis, but it is also insufficient for complete depolymerization. The combination of the two treatments, i.e. moderate chemical hydrolysis (0.2 M H2SO4, 80°C, 48 h) combined with enzymatic hydrolysis is not more effective compared to chemical hydrolysis in drastic conditions (2 M H2SO4 at 100°C). The strong interaction between the neutral and acid fractions of flaxseed mucilage may hinder total release of sugar residues. Physical treatment prior to the hydrolysis could be necessary to achieve complete depolymerisation of flaxseed mucilage

Ripening influences banana and plantain peels composition and energy content

Musa sp. peels are widely used by smallholders as complementary feeds for cattle in the tropics. A study of the influence of the variety and the maturation stage of the fruit on fermentability and metabolisable energy (ME) content of the peels was performed using banana (Yangambi Km5) and plantain (Big Ebanga) peels at three stages of maturation in an in vitro model of the rumen. Peel samples were analysed for starch, free sugars and fibre composition. Samples were incubated in the presence of rumen fluid. Kinetics of gas production were modelled, ME content was calculated using prediction equation and short-chain fatty acids production and molar ratio were measured after 72 h of fermentation. Final gas production was higher in plantain (269–339 ml g−1) compared to banana (237–328 ml g−1) and plantain exhibited higher ME contents (8.9–9.7 MJ/kg of dry matter, DM) compared to banana (7.7–8.8 MJ/kg of DM). Butyrate molar ratio decreased with maturity of the peels. The main influence of the variety and the stage of maturation on all fermentation parameters as well as ME contents of the peels was correlated to changes in the carbohydrate fraction of the peels, including starch and fibre

Acidogenic fermentation of potato wastes to produce carboxylate platform chemicals : influence of cations used for pH control

Potato cropping and its industrial processing generate significant amounts of wastes/ residues which can be valorized for the sustainable production of value-added chemicals and energy (e.g. volatile fatty acids (VFAs) and biohydrogen) in biorefineries. These value-added products are produced through the acidogenic fermentation, which is a complex process influenced by several factors such as: temperature, pH, hydraulic retention time (HRT), organic loading rate, etc. In order to control the pH in semi-continuous bioreactors, we used three different carbonate salts (CaCO3, K2CO3 and Na2CO3), with the aim of assessing the potential inhibition effect of cations (Ca2+, K+, Na+) on the process while keeping the same anion (CO32-). Potato wastes were directly used with no physicochemical pretreatment and the acidogenic fermentation was monitored for 60 days under semi-continuous conditions. Maximum total VFA (tVFA) concentration was 24 g_COD/kg_mixed_liquor, and maximum yield of chemical oxygen demand (COD) conversion into tVFA was 42 % when the pH was neutralized by Na2CO3. Butyric, acetic and caproïc acid were the predominant VFA in all cases. The concentration of lactic acid was almost equal to caproïc acid concentration for the case of K2CO3. The difference in fermentation profile between the three used carbonate salts was not really significant. The amount of biohydrogen produced was about 22, 22 and 24 g_COD_H2/kg_mixed_liquor when the pH was neutralized by CaCO3, K2CO3 and Na2CO3, respectively

A multistage process to enhance cellobiose production from cellulosic materials

Cellobiose, a disaccharide, is a valuable product that can be obtained from cellulose hydrolysis. In this study, a simple methodology is presented to enhance the production and improve the selectivity of cellobiose during enzymatic hydrolysis of cellulose. The approach consisted of a multistage removal of filtrate via vacuum filtration and resuspension of the retentate. By this process, the remaining solid was further hydrolyzed without additional enzyme loading. Compared to the continuous hydrolysis process, the production of cellobiose increased by 45%. Increased selectivity of cellobiose is due to the loss of beta-glucosidases in the filtrate, while enhanced productivity is likely due to mitigated product inhibition