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White biotechnologies have several challenges to overcome in order to become a viable industrial process. Achieving highly concentrated lignocellulose materials and releasing fermentable substrates, with controlled kinetics in order to regulate micro-organism activity, present major technical and scientific bottlenecks. The degradation of the main polymeric fractions of lignocellulose into simpler molecules is a prerequisite for an integrated utilisation of this resource in a biorefinery concept. The characterisation methods and the observations developed for rheology, morphology, etc., that are reviewed here are strongly dependent on the fibrous nature of lignocellulose, are thus similar or constitute a good approach to filamentous culture broths. This review focuses on scientific works related to the study of the rheological behaviour of lignocellulose suspensions and their evolution during biocatalysis. In order to produce the targeted molecules (synthon), the lignocellulose substrates are converted by enzymatic degradation and are then metabolised by micro-organisms. The dynamics of the mechanisms is limited by coupled phenomena between flow, heat and mass transfers in regard to diffusion (within solid and liquid phases), convection (mixing, transfer coefficients, homogeneity) and specific inhibitors (concentration gradients). As lignocellulose suspensions consist of long entangled fibres for the matrix of industrial interest, they exhibit diverse and complex properties linked to this fibrous character (rheological, morphological, thermal, mechanical and biochemical parameters). Among the main variables to be studied, the rheological behaviour of such suspensions appears to be determinant for process efficiency. It is this behaviour that will determine the equipment to be used and the strategies applied (substrate and biocatalysis feed, mixing, etc.). This review provides an overview of (i) the rheological behaviour of fibrous materials in suspension, (ii) the methods and experimental conditions for their measurements, (iii) the main models used and (iv) their evolution during biocatalytic reactions with a focus on enzymatic hydrolysis.

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Carbon nanotubes (CNTs) were coated TiO 2 nanoparticles via sol-gel process using titanium tetra-isoproxide Ti[OCH(CH 3 ) 2 ] 4 (TTIP). The structure of TiO 2 /CNT hybrid samples was determined by x-ray diffractometer D5005 (Siemen) with CuKα radiation. Their morphology and sizes were investigated with FE-SEM and HR-TEM, which shows that nanoparticles were coated on CNTs. The UV-vis absorption results indicate interaction between TiO 2 and CNTs, the composite material can absorb at higher wavelength and the absorption even covers the whole range of visible region. By investigating different addition ratios of CNT on the photocatalytic activity of TiO 2 /CNTs, we find that the higher ratio in TiO 2 /CNT will decrease the photocatalytic activity. We have calculated the electronic structure of the anatase TiO 2 and single-wall carbon nanotube (SWCNT) by first-principles stimulation. We investigate the property in hybrid structure: molecular and small clusters of TiO 2 adsorbed on SWCNT support using density functional calculation. The energy and charge distribution calculations show that SWCNT can make TiO 2 clusters become more stable in the hybrid system.