Bioconversion efficiency

Previously, we have shown that functional secretion of OPH molecules into the periplasmic space induced about 2.8-fold higher specific whole cell OPH activity [10]. From the detail reaction kinetic studies in this work, we showed that this periplasmic space-secretion strategy provided much improved bioconversion capability and efficiency ( 1.8-fold) for Paraoxon as a model organophosphate compound. From these results, we confirmed that Tat-driven periplasmic secretion of OPH can be successfully employed to develop a whole cell biocatalysis system with notable enhanced bioconversion efficiency and capability for environmental toxic organophosphates. 

Inactivation of the biocatalyst owing to these effects can be a significant limitation for industrial application of enzymatic and whole-cell biotransformation. For more than 20 years, many attempts have been made to associate the toxicity of different solvents with some of their physicochemical properties and to explain the influence of the two-phase system composition on bioconversion efficiency. 

Maximum production of soyasapogenol B (about 152.3 mg/50 ml) was obtained using 1.5%(w/v) soybean saponin and 1.5%(w/v) glucose, at 32°C after 72 h at pH 7 using phosphate buffer. Under these optimal conditions, the bioconversion efficiency increased from 20.5 to 85.3%. The isolation of soyasapogenols... 

Biocatalytic ledox reactions offer great synthetic utility to organic chemists. The majority of oxidase-catalyzed preparative bioconversions are still performed using a whole-ceU technique, despite the fact that the presence of more than one oxidoreductase in cells often leads to product degradation and lower selectivity. Fortunately, several efficient cofactor regeneration systems have been developed (160), making some cell-free enzymatic bioconversions economically feasible (161,162). 

The development of bioreactor systems for the production of large-volume chemicals (see Chapter 3) could be the basis for reconsidering the production of biomass in limited quantities for fuel uses. This would require efficient microbial organisms to catalyze fermentation, digestion, and other bioconversion processes, as well as efficient separation methods to recover fuel products from process streams. 

Efficient bioconversion of sparingly water-soluble substrates. 

Efficiency of light energy bioconversion was calculated as the ratio between an energy accumulated in H2 produced by 1 cm2 of surface and an incident light energy. 

Thus, if the problem of low efficiency of light energy bioconversion will be solved, technological research with clean strategy and evident goals will produce real practical system in very near future after. However, even in this case, much experimental research should be done to optimize the whole system. 

The catalytic conversion of platform molecules produced by bioconversion of renewables into bioproducts. This is already the basis of many industrial processes, leading to important tonnages of chemicals and polymers from carbohydrates and triglycerides and fine chemicals from terpenes. This approach needs to be extended and process efficiency should be strengthened by designing more active and selective catalysts. 

Bioconversion platforms for lignocellulosics-to-ethanol are beginning to become commercially viable, but the effectiveness of the pretreatment stage should still be improved, the cost of the enzymatic hydrolysis stage decreased, and overall process efficiencies improved by better synergies between various process stages. There is also a need to improve process economics by creating co-products that can add revenue to the process. 

The most straightforward way of using sohd enzymes in organic media is to suspend the solid enzyme directly in the solvent. If one wants to get quick results from a bioconversion and does not want to optimise the efficiency of the enzyme, this method is the obvious first choice. There are many example in the hterature where enzymes have been used successfully in synthesis just as powders directly from the enzyme manufacturer. Sometimes there is a need to dissolve the enzyme powder and re-lyophilise it from a buffer with a more suitable composition, see the section 9.6 pH control in non-conventional media . 

The manner in which a bioconversion is performed is dictated by the nature of the biocatalyst, the chemistry, involved, and process economics.16 The overall aims of a bioconversion are the same as for any process, to maximize the production of a given material at the lowest overall cost. In some cases this might mean maximizing the volumetric productivity (Qp in units of mol.m3 s l) of the reactor. Alternately, it might be most important to enable the more efficient recovery through maximizing the ratio of desired to undesired products. If the cost of the biocatalyst is limiting then the catalyst productivity (P ) must be maximized, a function of the intrinsic activity of the catalyst itself and the fashion in which it is used. 

---