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This review article provides an updated critical literature review on the production and applications of Polyglutamic Acid (PGA). alpha-PGA is synthesized chemically, whereas gamma-PGA can be produced by a number of microbial species, most prominently various Bacilli. Great insight into the microbial formation of gamma-PGA has been gained thanks to the development of molecular biological techniques. Moreover, there is a great variety of applications for both isoforms of PGA, many of which have not been discovered until recently. These applications include: wastewater treatment, food products, drug delivery, medical adhesives, vaccines, PGA nanoparticles for on-site drug release in cancer chemotherapy, and tissue engineering.

Cellulosic nanomaterials provide a novel and sustainable platform for the production of high performance materials enabled by nanotechnology. Bacterial cellulose (BC) is a highly crystalline material and contains pure cellulose without lignin and hemicellulose. BC offers an opportunity to provide control of the products' properties in-situ, via specific BC production methods and culture conditions. The BC potential in advanced material applications are hindered by a limited knowledge of optimal BC production conditions, efficient process scale-up, separation methods, and purification methods. There is a growing body of work on the production of bacterial cellulose nanocrystals (BCNs) from BC fibers. However, there is limited information regarding the effect of BC fibers' characteristics on the production of nanocrystals. This review describes developments in BC and BCNs production methods and factors affecting their yield and physical characteristics.

Based on experimental results from a 7.6 cm I.D. and 3 m high liquidsolid circulating fluidized bed, the liquikolid circulating fluidization regime has been separated into two zones: the initial circulating fluidization zone and the fully developed circulating fluidization zone. The distinct hydrodynamic behavior and the influence of particle properties in the two circulating fluidization zones have been studied. The overall flow structure in LSCFB, although still somewhat non-uniform, is much more uniform than that in a gas-solid CFB. Our experimental results also show that the axial flow characteristics and the regime transition can be strongly affected by the particle density. The stable operation range of the circulating fluidization system and the influences of some associated factors, such as the solids inventory and the particle density, were also investigated for the first time.A partir de resultats experimentaux d'un lit fluidise circulant liquidesolides de 7,6 cm de diarnetre interieur et 3 m de haut, on a separe le regime de fluidisation circulant liquidesolides en deux zones : la zone de fluidisation circulante initiale et la zone de fluidisation circulante pleinement developpee. On a etudie le comportement hydrodynarnique distinct et l'influence des proprietes des particules dans deux zones de fluidisation circulantes. La structure globale de I'ecoulement dans deux zones de fluidisation circulantes. La structure globale de I'ecoulement dans le LSCFB, quoique toujours legerement non uniforme, est beaucoup plus uniforme que dans un CFB gaz-solides. Nos resultats experimentaux montrent egalement que les caracteristiques d'ecoulement axial et la transition de regime peuvent 6tre fortement influencees par la masse volumique des particules. La g a m e de fonctionnement stable du systeme de fluidisation circulant et I'influence de certains facteurs associes, comme I'inventaire des solides et la masse volumique des particules, ont egalement ete etudiees pourla premiere fois. When the liquid velocity is beyond the critical transition velocity, it would be necessary to separate the entrained particles at the riser top and recirculate them back to the base of the riser column. LSCFB has potential applications in the fields of food processing, biochemical processing, petrochemical and metallurgical processing, etc. (Di Felice, 1995; Liang et al., 1997).Hydrodynamics studies are important to properly design an industrial LSCFB system. The flow characteristics in a LSCFB system has been shown to be very different from a conventional liquid-solid fluidized bed and from a gassolid circulating fluidized bed, as reported in recent studies (Liang et al., 1996;1997). However, a more systematic study is still needed for a comprehensive understanding of the phenomena. For example, little work has been done concerning the effects of the physical properties of the particles, such as particle density, on the hydrodynamics of the system. When Liang et al. (1997) studied the solids flow with two relatively low-density particl...

There are many dynamic methods for measuring the volumetric mass transfer coefficient. The “gas out–gas in” method can directly determine the volumetric mass transfer coefficient in a bioreactor system and provide estimates of the volumetric microbial oxygen uptake rate and the average oxygen saturation concentration at the gas–liquid interface. The errors on these parameters are large if the dissolved oxygen probe response time is not considered. For reliable measurements, deconvolution of the oxygen probe measurements must be made. © 1995 John Wiley & Sons, Inc.