Enzyme productivity

Certain factors and product precursors are occasionally added to various fermentation media to iacrease product formation rates, the amount of product formed, or the type of product formed. Examples iaclude the addition of cobalt salts ia the vitamin fermentation, and phenylacetic acid and phenoxyacetic acid for the penicillin G (hen ylpenicillin) and penicillin V (phenoxymethylpenicillin) fermentations, respectively. Biotin is often added to the citric acid fermentation to enhance productivity and the addition of P-ionone vastly iacreases beta-carotene fermentation yields. Also, iaducers play an important role ia some enzyme production fermentations, and specific metaboHc inhibitors often block certain enzymatic steps that result in product accumulation. 

The new Uquid laundry detergents, with no phosphates, have developed a use for alkan olamines. In nonenzyme formulations, they contribute alkalinity, pH control, and enhanced product stabiUty. In enzyme products, alkan olamines contribute to the stabiUty of the enzyme in water solutions (107). 

When selecting a suitable feed symp, the main criteria are optimization of enzyme productivity and minimization of the formation of by-products. Typical feed symp specifications are shown in Table 5. Higher symp concentration and higher viscosity results in a reduced isomerization rate due to diffusion resistance in the pores of the immobilized enzyme. A deaeration step is desirable to remove dissolved oxygen that would otherwise iacrease the formation of by-products. The pH is adjusted to the optimum level for the productivity of the enzyme. 

The term biotransformation or biocatalysis is used for processes in which a starting material (precursor) is converted into the desired product in just one step. This can be done by use either of whole cells or of (partially) purified enzymes. Product examples range from bulk chemicals (such as acrylamide) to fine chemicals and chiral synthons (chiral amines or alcohols, for example). There are several books and reviews dealing with the use of bio transformations either at laboratory or at industrial scales [1, 10-13]. 

Li, Z., and Meighen, E. A. (1994). The turnover of bacterial luciferase is limited by a slow decomposition of the ternary enzyme-product complex of luciferase, FMN, and fatty acid. J. Biol. Chem. 269 6640-6644. 

Immobilized system the air circulates over a film of microorganisms that grows on a solid surface. In an immobilized bioreactor, particulate biocatalysts for enzyme production and conversion of penicillin to 6-aminopenicillanic acid are used. 

In downstream processing of a fermentation unit for enzyme production with a feed stream of sugar- at a concentration of 35 g-l the expected product to be recovered is a-amylase. 

Enzyme production by growth of T. viride on pretreated cellulose. 

Several potential and mutant strains of T. viride have been identified in SCP production. Their capacity for amyloletic enzyme production was enhanced severalfold in SCP from lingnocellulosic resources. The process of bioconversion of agricultural wastes to SCP appeared to be too complex to find an economic application for agricultural waste. 

Enzyme (A) + substrate (B) o enzyme-substrate complex (AB) o enzyme-product complex (AC) enzyme (A) + product (C)... 

The advantages of such biotransformation processes are (1) the relatively high yields which can be achieved with specific enzymes, (2) the formation of chiral compounds suitable for biopharmaceuticals, and (3) the relatively mild reaction conditions. Key issues in industrial-scale process development are achieving high product concentrations, yields and productivities by maintaining enzyme activity and stability under reaction conditions while reducing enzyme production costs. 

Amylase enters the blood largely via the lymphatics. An increase in hydrostatic pressure in the pancreatic ducts leads to a fairly prompt rise in the amylase concentration of the blood. Neither an increase in volume flow of pancreatic juice nor stimulation of pancreatic enzyme production will cause an increase in senm enzyme concentration. Elevation of intraductal pressure is the important determinant. Stimulation of flow in the face of obstruction can, however, augment the entry of amylase into the blood, as can disruption of acinar cells and ducts. A functional pancreas must be present for the serum amylase to rise. Serum amylase determination is indicated in acute pancreatitis in patients with acute abdominal pain where the clinical findings are not typical of other diseases such as appendicitis, cholecystitis, peptic ulcer, vascular disease or intestinal obstruction. In acute pancreatitis, the serum amylase starts to rise within a few hours simultaneously with the onset of symptoms and remains elevated for 2 to 3 days after which it returns to normal. The peak level is reached within 24 hours. Absence of increase in serum amylase in first 24 hours after the onset of symptoms is evidence against a diagnosis of acute pancreatitis (76). 

Action pattern analyses of pectin degradation. HPAEC data of oligomers released from 68% esterified pectin by combinations of Eca PLs are graphically represented. Arrows indicate addition of the third enzyme. Products with degrees of polymerization ranging from 2 to 9 were detected. The graphs illustrate the generation of dimers (A), trimers ( ) and pentamers ( ). 

Weber J, Wegener C (1986) Virulence and enzyme production of Erwinia carotovora ssp. atroseptica on potato tuber tissue. J Phytopathol 117 97-106... 

Addition of rice bran to the solid substrates to make the ratio of wheat bran, rice bran and rice husk to 9 9 2 helped increasing the activity of pectinases from Rhizopus sp. 26R as shown in Figure 4. The activity of the enzyme was approx. 4.3 times higher. Moreover, either 1 g of pectin or 0.5 g of yeast extract did not help increasing of the enzyme production. In contrary, the enz5mie activity was decreased 2.6 times to that of the former one. Addition of raw cassava starch to the substrates did no effect to the enzyme production (data not shown). 

Different ratios of the solid substrates, wheat bran, rice bran and rice husk, were done and the activity of the pectinases was compared in Figure 5. The mixture of wheat bran, rice bran and rice husk in the ratios of 9 9 2 or 6 12 2 appeared to be two of the best composition ratios for growth of the fungus and the pectinase production.The ratio of 6 12 2 was selected for the enzyme production since rice bran was cheaper than wheat bran and locally obtained. 

Using agricultural wastes as solid substrates for the production of pectinase from Rhizopus sp. 26R gave benefit, not only to the utilization of the wastes but also to the reduction of the cost of the enzyme production. 

The enzyme production in the solid substrates composed of wheat bran and rice husk (18 2) could be increased by the addition of either 1 g raw cassava starch or 1 g pectin to a 20 g substrates. The enzyme activity increased approx. 1.7 and 2.4 times, respectively. 

Cost of the enzyme production in solid substrate was estimated to be US 180 for 10 million units of crude pectinase. This price included the production of fungal spore inoculum. This production of pectinases from Rhizopus sp. 26R using agricultural wastes as solid substrates was one of the way to utilize agricultural wastes to value-added products and the cost of the enzyme production was very reductive. 

The screening method based on diameter of halos yielded only five strains with at least 20% more PG than wild t> e. Most attempts to enhance pectinase production have been made in filamentous fiingi, in which enzyme production is regulated by induction and catabolite repression mechanisms [8], By contrast, PG produced by marxianus is constitutive and not subject to catabolite repression [6], Failure to find greatly enhanced secretion levels is consistent with the idea of a constitutive gene that is capable of only modest further induction. PG was found in this study to be already the most prolific secreted protein of K. marxianus. 

Protoplast fusion induced by polyethyleneglycol and Ca was carried out between two auxotrophic mutants of Aspergillus sp. CH-Y-1043. The hybrids obtained showed significant differences in endopectinase activity and morphology compared to the prototrophic strain. Strains grown on lemon peel showed production improvement with respect to the parental strain. Since H15 hybrid showed up to 90% higher endopectinase production than the wild type CH-Y-1043, kinetics of enzyme production in Fernbach flasks and Fermentor (14L) by H15 were determined. 

Of the total, twenty six hybrids were assayed for endo-pectinase production on lemon peel, because we are interested in the enzyme production from this raw material. The relative activity of the hybrids with respect to Aspergillus sp. CH-Y-1043 is presented in Table 2. The highest increases (up to 46%) were observed in H5, H6, H15, Hll, H13, H14, HIO and H25 hybrids. In some hybrids, lower values of endopectinases production with respect to parental strain were obtained. 

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