A New Approach to Produce Succinic Acid Through a Co-Culture System.

Microorganisms can produce a wide range of bio-based chemicals that can be used in various industrial applications as molecules of interest. In the present work, an analysis of the power production by pure culture, co-culture, and sequential culture was performed. In this study, both the mono-culture and the co-culture strategies of Actinobacillus succinogenes with Saccharomyces cerevisiae as carbon sources to produce succinic acid using glucose and fructose were examined. The cultures were performed in batch mode and a great attention was paid to the co-culture system to improve the biosynthetic pathway between A. succinogenes and S. cerevisiae by combining these two strains in a single fermentation process. Under microaerobic and anaerobic conditions, the process was characterized in terms of sugars concentration, cell density, metabolites, yield (mol-C products/ mol-C sugars), the temperature conditions for productivity, and pH. The results showed that the process could consume glucose and fructose and could adapt to different concentrations of the two sugars more quickly than by a single organism and the best results were obtained in a sequential co-culture recording 0.27 mol L-1 of succinic acid concentration and a volumetric productivity of 0.3 g L-1 h-1. Under the investigated operating conditions, the combination of these two strains in a single reactor produced a significant amount of succinic acid (0.70 mol-C SA/mol-C substrates). A simultaneous and sequential co-culture strategy can be a powerful new approach in the field of bio-based chemical production.

Luminescence Amplification at BiVO4 Photoanodes by Photoinduced Electrochemiluminescence.

Photoinduced electrochemiluminescence (PECL) combines semiconductor (SC) photoelectrochemistry with electrochemiluminescence (ECL). In PECL, the incident light is converted into a different wavelength by an electrochemical reaction at a SC photoelectrode and allows triggering of ECL at low potentials. This concept has been employed to design up-conversion systems. However, PECL strongly suffers from the photoelectrochemical instability of these low band gap SCs. Reported here for the first time is an original light-conversion strategy based on PECL of a luminol derivative (L-012) at BiVO4 photoanodes in water. Incident light photoexcites simultaneously the L-012 fluorescence and the photoanode. However, the resulting signal is surpassed by the PECL emission. PECL can be induced at a potential as low as -0.4 V for several hours and can be employed to finely tune L-012 luminescence. This finding is promising for the design of new analytical strategies and light-addressable systems.

Valorization of carob waste: Definition of a second-generation bioethanol production process.

The aim of this work was to develop a strategy for second-generation ethanol production from carob solid waste issued from Lebanese food industry. The pros and cons of submerged (SF) and solid-state fermentations (SSF) using S. cerevisiae on ethanol yield and productivity were compared, including the respective roles of upstream and downstream processes, such as the size reduction, or sugar and ethanol recovery processes. The design of experiments methodology was applied. Experimental results demonstrated that SSF applied to cut carob waste from carob syrup preparation was simpler to operate and more cost-effective, maintained yield and productivity (0.458g ethanol/g consumed sugar and 4.3g/(kg waste)/h) in comparison to SF (0.450g ethanol/g consumed sugar and 5.7g/(kg waste)/h), and was able to achieve ethanol production up to 155g/(kg waste) at low water demand, while SF reached only 78g/(kg waste) due to the limitations of the sugar extraction pretreatment.