Batch fermentation of d-glucose/cellobiose mixtures by clostridium acetobutylicum atcc 824: energetic and carbon source regulation

Lignocellulosic biomass presents an interesting alternative to fossil carbon sources as a source of renewable energy that respects the environment. Indeed, this abundant resource can be converted by a wide range of thermal, chemical and biological techniques to compounds that can be used as substrate in anaerobic fermentation to produce biofuels and building blocks. As a general rule, micro-organisms possess regulation mechanisms that ensure the sequential use of the carbon and energy sources present in their environment. These regulations may consequently play a vital role in biomass to energy and building blocks conversion performances. Clostridium acetobutylicum, a promising biomass transformation organism, has the capacity to utilize a wide variety of compounds as carbon and energy sources. These compounds may be present in a complex mixture produced from cellulose conversion. Therefore it is of high importance to understand the potential synergy or inhibiting effects of the cellulose-derived products. The aim of this work is to study this regulation mechanism by using glucose and cellobiose as model substrates, provided alone and in mixtures to Clostridium acetobutylicum. Our experiments show a total consumption of both substrates, alone or in mixtures, with an increment of 30% of microbial growth production of cellobiose over glucose. A diauxic growth (cell growth in two phases) occurs in the presence of different mixtures of D-glucose and cellobiose. In general, D-glucose is the preferred substrate and after its complete consumption, when exhausted, the growth kinetics exhibits an adaptation time, of approximately 1-2 hours, before to be able to use cellobiose (figure 1). This adaptation is probably due to an induction stage that is also accompanied of acid consumption (lactic acid). This study provides a first approach to understand the metabolic changes related to substrate utilization in Clostridia. Please click Additional Files below to see the full abstract

Cellulose valorization in biorefinery: integration of fast pyrolysis and fermentation for building blocks production

A combination of thermochemical and biological conversion of cellulosic materials is a promising alternative for the production of biofuels and building blocks in an integrated biorefinery. Indeed, enzymatic depolymerization is selective but slow and expensive. It would be of interest to associate thermochemical conversion for a fast depolymerization of biomass with biochemical conversion for a selective conversion of depolymerized liquid streams. In this work, cellulose is pyrolyzed to produce sugars that can be used as substrate for a fermentation process. This work is the result of a scientific collaboration between ICFAR (London, Canada) and CNRS (Nancy, France). Pyrolysis was performed in a fluidized bed reactor at 475ᵒC with a bio-oil yield of 73.4 wt.% (Figure 1). Different fractions of bio-oil were recovered with a set of 5 condensers. Levoglucosan and total sugars were quantified by GC-FID-MS and phenol/sulphuric acid method respectively. The maximum yields of levoglucosan (43.7 %) and total sugars (80.4 %) were found in the first condenser that was kept at 70ᵒC. Due to the non-fermentable condition of levoglucosan, all the oil fractions, as well as a mixture of them, were hydrolyzed to obtain fermentable glucose. The different bio-oil fractions and a mixture of all fractions were used as substrate in a fermentation reactor to produce acetone, butanol and ethanol (ABE). The talk will present the mass yields obtained for the integrated process combining pyrolysis, hydrolysis and fermentation (figure 2). The microorganisms were not able to grow in the mixture of all fractions. On the contrary, fractions from condenser 1 and 2 lead to normal bacterial growth and fermentation products pattern. Maximum yields (per gram of oil) of acetone=4.6 %, butanol=13.2 % and ethanol=0.1 % were found for the bio-oil collected in the first condenser. These results put in evidence the importance of pyrolysis with staged condensation as an entry for fermentation processes. The methodology proposed in this work could be applied to other biochemical conversion of bio-oils to produce higher added-value products. Please click Additional Files below to see the full abstract

Herpes simplex virus and varicella zoster virus, the house guests who never leave.

Human alphaherpesviruses including herpes simplex viruses (HSV-1, HSV-2) and varicella zoster virus (VZV) establish persistent latent infection in sensory neurons for the life of the host. All three viruses have the potential to reactivate causing recurrent disease. Regardless of the homology between the different virus strains, the three viruses are characterized by varying pathologies. This review will highlight the differences in infection pattern, immune response, and pathogenesis associated with HSV-1 and VZV

Cross-validation of ELISA and a portable surface plasmon resonance instrument for IgG antibody serology with SARS-CoV-2 positive individuals.

We report on the development of surface plasmon resonance (SPR) sensors and matching ELISAs for the detection of nucleocapsid and spike antibodies specific to the novel coronavirus 2019 (SARS-CoV-2) in human serum, plasma and dried blood spots (DBS)

Diauxic growth of Clostridium acetobutylicum ATCC 824 when grown on mixtures of glucose and cellobiose

Abstract Clostridium acetobutylicum, a promising organism for biomass transformation, has the capacity to utilize a wide variety of carbon sources. During pre-treatments of (ligno) cellulose through thermic and/or enzymatic processes, complex mixtures of oligo saccharides with beta 1,4-glycosidic bonds can be produced. In this paper, the capability of C. acetobutylicum to ferment glucose and cellobiose, alone and in mixtures was studied. Kinetic studies indicated that a diauxic growth occurs when both glucose and cellobiose are present in the medium. In mixtures, d-glucose is the preferred substrate even if cells were pre grown with cellobiose as the substrate. After the complete consumption of glucose, the growth kinetics exhibits an adaptation time, of few hours, before to be able to use cellobiose. Because of this diauxic phenomenon, the nature of the carbon source deriving from a cellulose hydrolysis pre-treatment could strongly influence the kinetic performances of a fermentation process with C. acetobutylicum

Hydrothermal conversion of wood, organosolv and chlorite pulps

International audienc

Decomposition of Cellulose in Hot-Compressed Water: Detailed Analysis of the Products and Effect of Operating Conditions

Understanding the reaction pathways of cellulose hydrolysis in hot-compressed water (HCW) is crucial for the optimization of fermentable sugar and chemical production. Advanced analytical strategies are required to better assess the wide range of products from cellulose conversion in HCW. In this work, cellulose conversion in HCW was conducted in an autoclave with sampling upon the reaction time under isothermal conditions (180, 220, and 260 °C from 0 to 120 min). Total water-soluble carbohydrates were quantified (phenol/sulfuric acid method). These products were first characterized by size-exclusion chromatography coupled to evaporative light scattering detection and mass spectrometry (SEC–ELSD–MS). SEC is useful for screening the molecular weight distribution of soluble products. Then, the chemical structure of water solubles has been attributed by hydrophilic interaction liquid chromatography coupled to a linear trap quadrupole Orbitrap mass spectrometer (HILIC–LTQ–Orbitrap–MS). This method notably provides evidence of the formation of a cellobiose conformer under some HCW conditions. A specific high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC–PAD) method has been developed. This method allows for a selective separation of 5-hydroxymethylfurfural (5-HMF), glucose, fructose, mannose, and oligomers up to cellopentaose. Carboxylic acids were quantified by high-performance liquid chromatography with ultraviolet detection (HPLC–UV). Solid residues obtained after HCW conversion were characterized by X-ray diffraction (XRD) and permanent gas by micro-gas chromatography. The global reaction mechanism of cellulose liquefaction in HCW is rationalized on the basis of these complementary methods. Cellulose conversion first proceeds with heterogeneous hydrolysis (fiber surface) to produce soluble oligomers in competition with pyrolysis (inner fibers with limited mass transfer of water), producing levoglucosan (promoted at a higher temperature). Soluble oligomers produce glucose and isomers by homogeneous hydrolysis (liquid phase). C₆ sugars can then undergo further conversion to produce notably 5-HMF and erythrose

Blood Flow and Shear Stress Allow Monitoring of Progression and Prognosis of Tumor Diseases

International audienceIn the presence of tumor angiogenesis, blood flow must increase, leading to an elevation of blood flow velocities (BFVels) and wall shear stress (WSS) in upstream native arteries. An adaptive arterial remodeling is stimulated, whose purpose lies in the enlargement of the arterial inner diameter, aiming for normalization of BFVels and WSS. Remodeling engages delayed processes that are efficient only several weeks/months after initiation, independent from those governing expansion of the neovascular network. Therefore, during tumor expansion, there is a time interval during which elevation of BFVels and WSS could reflect disease progression. Conversely, during the period of stability, BFVels and WSS drop back to normal values due to the achievement of remodeling processes. Ovarian peritoneal carcinomatosis (OPC), pseudomyxoma peritonei (PMP), and superficial arteriovenous malformations (AVMs) are diseases characterized by the development of abnormal vascular networks developed on native ones. In OPC and PMP, preoperative blood flow in the superior mesenteric artery (SMA) correlated with the per-operative peritoneal carcinomatosis index (OPC: n = 21, R = 0.79, p < 0.0001, PMP: n = 66, R = 0.63, p < 0.0001). Moreover, 1 year after surgery, WSS in the SMA helped in distinguishing patients with PMP from those without disease progression [ROC-curve analysis, AUC = 0.978 (0.902–0.999), p < 0.0001, sensitivity: 100.0%, specificity: 93.5%, cutoff: 12.1 dynes/cm 2 ]. Similarly, WSS in the ipsilateral afferent arteries close to the lesion distinguished stable from progressive AVM [ROC-curve analysis, AUC: 0.988, (0.919–1.000), p < 0.0001, sensitivity: 93.5%, specificity: 95.7%; cutoff: 26.5 dynes/cm 2 ]. Blood flow volume is indicative of the tumor burden in OPC and PMP, and WSS represents an early sensitive and specific vascular marker of disease progression in PMP and AVM