Extracellular production

Fig. 2. Schematic representation of a fermentation process for an extracellular product.

In whole cell bioprocesses, extracellular products are preferable because this removes the requirement for cell disruption and tins reduces the level of impurities in the product solution. Nevertheless, product isolation and purification can be prohibitively expensive particularly for low concentration product streams, which is a feature of many bioprocesses. 

The solid cuticle of the arthropod is a complex extracellular product made of chitin (a polysaccharide) and tanned or fibrous proteins, and is often hard and... 

Choi, J.H. and Lee, S.Y. (2004) Secretory and extracellular production of recombinant proteins using Pichia pastoris. Applied Microbiology and Biotechnology, 64 (5), 625-635. 

Kajino, T., Saito, Y., Asami, O. etal. (1997) Extracellular production of an intact and biologically active human growth hormone by the Bacillus brevis system. Journal of Industrial Microbiology Biotechnology, 19 (4), 227-231. 

The presence of foreign protein in the medium of plant cultures does not necessarily mean that all or even most of the product can be recovered from the medium. In many expression systems where an appropriate signal sequence has been used, considerable amounts of foreign protein remain within the plant cells and/or tissues. For example, in a comparison of IgG antibody production in tobacco cell suspension and hairy root cultures, a maximum of 72% of the total antibody was found in the medium of the suspension cultures whereas only 26% was found in the medium of the hairy root cultures [17]. This result could indicate that secretion and/or transport across the cell wall was slower in the hairy roots alternatively, it could indicate poorer stability of the secreted protein in the hairy root medium. If foreign proteins are to be purified from the medium, improved secretion and extracellular product stability are desirable. 

The vast bulk of proteins synthesized naturally by E. coli (i.e. its homologous proteins) are intracellular. Few are exported to the periplasmic space or released as true extracellular proteins. Heterologous proteins expressed in E. coli thus invariably accumulate in the cell cytoplasm. Intracellular protein production complicates downstream processing (relative to extracellular production) as ... 

Targeted extracellular recombinant production generally results in low-level extracellular accumulation of the desired protein (often in the milligram per litre range). Extracellular production simplifies subsequent downstream processing, as discussed later in this chapter. 

Extracellular or intracellular nature of product. If the biopharmaceutical is an extracellular product then the less complex the media composition the better, in order to render subsequent product purification as straightforward as possible. 

All the pectin lyases so far described are of fungal origin and are secreted extracellularly. Production of pectin lyase by Rhizoctonia solani, Botrytis cinerea, and Fusarium oxysporum f. lycopersici was induced by pectate with D-glucose,265 pectin showing a lower inductive effect.231... 

Hydroxamates have been observed in the water in the Bay of Quinte, a eutrophic bay of Lake Ontario, and are believed to be produced by blue-green algae (76). Simpson and Neilands (77) have identified schizokinen, a hydroxamic acid derivative of citric acid as an extracellular product of the blue-green algae, Anabaena sp. However, not all Anabaena produce hydroxamates, Walsby (78) has shown that Anabaena cylindrica releases a large pigmented, peptide-containing material which complexes iron. As yet these peptides have not been examined for ability to complex the actinides. 

Robinson et al. (79) have demonstrated that extracellular products present in the media of microorganisms originally isolated from soil can alter the elution of plutonium on gel chromatograms and the mobility of plutonium on thin layer chromatograms. 

Exo-l,4-j8-D-xylosidases (EC 3.2.1.37) hydrolyze xylooligosaccharides and xylobiose to xylose by removing successive D-xylose residues from the nonreducing termini. j8-Xylosidase is part of most microbial xylanolytic systems, but the highest extracellular production levels have been reported for fungi. 

Algal extracellular products, present in great quantities during blooms,... 

Similar approaches to cloning of bacterial xylanases have been used for genes from Clostridium acetobutylicum (30), Bacillus polymyxa (31), Bacteroides succinogenes (32), Clostridium thermocellum (33) and Pseudomonas fluorescens subsp. cellulosa (34). In each case the xylanases were predominantly located intracellularly and the levels of xylanases produced from cloned systems were, in general, very low in comparison to yeast and fungal systems. A comparison of the production yields and extent of extracellular production for various cloned xylanase genes is found in Table... 

The fermentation products can be the cells themselves (biomass), components within the fermentation broth (extracellular), or those trapped in cells (intracellular), examples of which are listed in Table 10.1. As shown in Figure 10.1, if the product of our interest is the cell, cells are separated from the fermentation broth and then washed and dried. In the case of extracellular products, after the cells are separated, products in the dilute aqueous medium need to be recovered and purified. The intracellular products can be released by rupturing the cells and then they can be recovered and purified. The downstream processing for enzyme reactions will be similar to the process for extracellular products. 

Fogg, G. E. 1971. Extracellular products of algae in freshwaters. Archiv fiir Hydrobiologie 5 1-25. 

Fogg, G. E. 1983. The ecological significance of extracellular products of phytoplankton photosynthesis. Botanica Marina 26 3-14. 

Hama, T., and N. Handa. 1987. Pattern of organic matter production by natural phytoplankton population in a eutrophic lake. 2. Extracellular products. Archiv fur Hydrobiologie 109 227-243. 

Hellebust, J. A. 1974. Extracellular products. In Algal Physiology and Biochemistry (W. D. P. Stewart, Ed.), pp. 838-863. Univ. of California Press, Berkeley. 

Iturriaga, R., and A. Zsolnay. 1983. Heterotrophic uptake and transformation of phytoplankton extracellular products. Botanica Marina 26 375—381. 

Nalewajko, C., K. Lee, and P. Fay. 1980. Significance of algal extracellular products to bacteria in lakes and in cultures. Microbial Ecology 6 199-207. 

Fogg, G.E. and Westlake, D.F. (1955) The importance of extracellular products of algae in freshwater. Proc. Int. Assoc. Theor. Appl. Limnol., 12, 219-232. 

Myklestad, S.M. (1995) Release of extracellular products by phytoplankton with special emphasis on polysaccharides. Sci. Total Environ., 165, 155-164. 

All carbon sources tested have favored extracellular production of active surface agent by B. subtilis ATCC 6633, which was estimated by the reduction in surface tension of the fermented broth. However, except for stillage, there was no relationship between cell growth and biosurfactant production. Similar results were reported by other investigators (21,32,33) not only with B. subtilis strains, but also with other species of bacteria. The... 

Besides biomass and C02, no significant amount of extracellular products was detected. Xylitol and arabitol were only accumulated in small amounts, with a maximum of 2.0 and 3.8 g/L, respectively. Other metabolic products usually associated with the pentose metabolism of D. hansenii, such as ethanol and glycerol (46,47), were only found in trace amounts, less than 0.5 and 0.3 g/L, respectively. 

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