Biomass cellular

Initially fermentation broth has to be characterised on the viscosity of the fluid. If the presence of the biomass or cells causes trouble, they have to be removed. Tire product is stored inside the cells, the cells must be ruptured and the product must be freed. Intracellular protein can easily be precipitated, settled or filtered. In fact the product in diluted broth may not be economical enough for efficient recovery. Enrichment of the product from the bioreactor effluents for increasing product concentration may reduce the cost of product recovery. There are several economical methods for pure product recovery, such as crystallisation of the product from the concentrated broth or liquid phase. Even small amounts of cellular proteins can be lyophilised or dried from crude solution of biological products such as hormone or enzymes.2,3... 

Cell Walls (CW). After the extraction of the cellular enzymes from the biomass, the residue of homogenized cells was repeatedly washed with water and finally with 96 % ethanol, dried and the dry weight of cell walls was determined (10). 

Fig. 3 A, B. A Time courses of cellular poly(3HB) content during the accumulation phase plotted for various specific poly(3HB) formation rates. B Amount of poly(3HB) as a multiple of the residual biomass at different poly(3HB) contents... 

Fed-batch fermentations with P. oleovorans have been carried out using octa-nol and octanoate as substrate [53]. To ensure high oxygen transfer rates pure oxygen was used. With octanoate as substrate 41.8 g 1 1 biomass with a cellular PHA content of 37 % and a productivity of 0.34 g l"1 were reached. Higher biomass concentrations could not be achieved due to accumulation of the toxic octanoate. 

The qCC>2 is often used as an indicator of whether the microbial biomass is under stress. In general, factors that decrease the size of the microbial biomass tend to increase qC02. That is, factors that cause stress to the microbial community tend to reduce its size. Other factors could also contribute to an increased qC02. For example, bacterial communities are less efficient at converting substrate C into cellular C than fungi (Sakamoto and Oba 1994) so a change in the composition of microbial biomass can alter qC02 values. 

Using nonviable cellular biomass for azo dye removal has some advantages, namely the ability to function under extreme conditions of temperature and pH, and without addition of growth nutrients [10]. Also, waste yeast biomass, which is a by-product of industrial fermentations such as beer production, can be used as a relatively cheap source for biosorption of azo dyes. An important setback is the fact that the use of biomass for dye removal leads to an increase in the sludge amount, which requires further removal and treatment. 

The principal controls on the microbial reaction rate in our example, then, are biomass and thermodynamic drive (Fig. 33.2). Initially, in the presence of abundant lactate and arsenate, the rate is controlled by the size of the microbial population available to catalyze lactate oxidation. As the population increases, so does reaction rate. Later, as reactants are consumed and products accumulate, the reaction approaches the point at which the energy liberated by its progress is balanced by that needed in the cell to synthesize ATR Reaction rate is governed now by the energy available to drive forward the cellular metabolism, this energy represented by the thermodynamic potential factor Ft over the course of the experiment, the kinetic factors Fd and Fa play minor roles. 

The effect of phosphate on alkaloid production has also been evaluated (138). Using a modified induction medium devoid of phosphate and other essential growth factors, production of secondary compounds was more rapid than when phosphate was present. A broader study of the phenomenon has been reported by a French group (139) where, using three alkaloids as markers, the disappearance of the major nutrients from the medium and the evolution of phosphates, nitrates, ammonium ions, glucose, and starch in the cells were observed over time. It was not possible to relate alkaloid accumulation to the appearance or disappearance of any one metabolite in particular. However, other workers have found that the rate of biomass accumulation was directly related to the rate of formation of cellular serpentine (40) (140). 

This model may be criticised in two respects, respectively that the materials referred to are not quantifiable in a precise way (Esener et al.m), and that there is no account taken of the dilution effect on the intra-cellular material by the expansion of the biomass (FREDRICKSON1 91). In respect of the latter item, a... 

The last term in equation 5.245 represents the dilution of active component /, by the expansion of the biomass. Esener et al.m also present a two-compartment model which takes this effect into account and they emphasise the need to devise the theory so that it can be tested by experiment. In their model they identify a K compartment of the biomass which comprised the RNA and other small cellular molecules. The other compartment contained the larger genetic material, enzymes, and structural material. The model assumes that the substrate is absorbed by the cell to produce, in the first instance, K material, and thence it is transformed into G material. Additionally, the G material can be reconverted to K material, a feature intended to account for the maintenance requirement of the micro-organism. A series of material balances for the cellular components during growth in a CSTF produced the following differential equations ... 

With respect to the hydrolysis step, it can be accomplished by acid, by enzymatic, or by direct microbial attack. Microbial hydrolysis results primarily in the production of cellular biomass or single-cell protein. Acid hydrolysis, while simple and direct, results in a sugar syrup with considerable contamination from the side reaction products. Enzymatic hydrolysis is usually the cleanest hydrolysis process. Unfortunately, it is the most costly of the three to operate. 

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