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International audience; Palm sap collected (sugary juice) from palm trees is very widespread in the intertropical regions of Asia, America and Africa. This study aimed to evaluate the use of kefir grains and ferments as starters for the fermentation of fresh palm sap (PS) from Borassus aethiopum Mart. to produce new kefir-like beverages (KLBs). The batch fermentation was performed statically at room temperature (22 °C) during 48 h. Physicochemical analysis were performed using standard and HPLC methods. The KLBs (kefir-like beverages) from PS showed low ethanol and glycerol contents ranging from 0.84 ± 0.14 to 17.30 ± 2.06 g/L (0.07 to 1.38% v/v) and 0 to 0.67 g/L respectively. The pH value decreased significantly during 24 h of fermentation and ranging from 3.98 to 4.40 at the end of fermentation. The organic acids (lactate, acetate, propionate, citrate, succinate and pyruvate) were detected in KLBs from PS. There was an increase in the content of lactate, acetate, propionate and succinate during fermentation process, except citrate content. Lactate and acetate content reached maximum values ranging between 5.18 and 9.31 g/L, 0.94 and 1.69 g/L respectively. Sucrose concentration decreased significantly and reached a value ranging from 0 to 0.84 g/L, except in KLBs fermented using milk ferments (9.45 g/L). The study showed that water and milk kefir grains as well as kefir ferments were well adapted to ferment Borassus aethiopum Mart. fresh sap for KLBs production. Palm sap could be an ideal alternative base substrate to produce non-dairy probiotic fermented beverage with low ethanol and sugar contents.

The aim of this study was to investigate ammonia load removable by a fixed-bed bioreactor. In this study, high ammonia loads, up to 4.5 kgN/m3 d were applied on a fixed bed reactor colonised by two pures nitrifying bacteria: Nitrosomonas europaea ATCC® 19718 and Nitrobacter winogradskyi ATCC® 25391. The loads were similar to the highest values reported in literature especially with a two bacteria population. The complete ammonia removal efficiency in our installation has reached 2.5 kgN/m3.d for a full nitrification. An N-tank in series model was used to represent the fixed bed reactor and to predict the nitrification in the installation. The developed model was accurate and representative of the nitrification assumed by Nitrosomonas europaea ATCC® 19718 and Nitrobacter winogradskyi ATCC® 25391. This model was also used to predict the biomass and oxygen concentrations during the experiment under various operational conditions. The biofilm fixed on the solid support (polysterene beads 2 mm diameter) was mainly present in the bottom of the reactor where the ammonia load was applied. It is demonstrated that in this region of the column the oxygen concentrations reached the lowest values.

The aim of the present work was to study the growth of two nitrifying bacteria. For modelling the nitrifying subsystem of the MELiSSA loop, Nitrosomonas europaea ATCC® 19718 and Nitrobacter winogradskyi ATCC® 25931 were grown separately and in cocultures. The kinetic parameters of a stoichiometric mass balanced Pirt model were identified: μ max = 0.054 h −1 , decay rate b = 0.003 h −1 and maintenance rate m = 0.135 gN-NH 4 + ·gX −1 ·h −1 for Nitrosomonas europaea ; μ max = 0.024 h −1 , b = 0.001 h −1 and m = 0.467 gN-NO 2 − ·gX −1 ·h −1 for Nitrobacter winogradskyi . A predictive structured model of nitrification in co-culture was developed. The online evolution of the addition of KOH is correlated to the nitritation; the dissolved oxygen concentration is correlated to both nitritation and nitratation. The model suitably represents these two variables so that transient partial nitrification is assessed. This is a clue for avoiding partial nitrification by predictive functional control.