Microbially Produced Proteins

A few reports in the literature describe the effects of using peanut protein in comminuted meat systems such as meat loaves (, 64), frankfurters (6 ), and ground beef patties 66). In some instances, peanut protein either produced beneficial effects (e.g., increased tenderness and cohesiveness, 66) or no adverse effects from a sensory, physical, or microbial standpoint ( ). 

Ammonium sulfate is frequently used for protein precipitation, due to its high solubility in water, which allows the solvent to reach very high ionic strengths. Usually, protein precipitates produced through salting-out do not denature and the protein activity is easily recovered. Addition of neutral salts can also protect proteins against proteolysis and microbial contamination. 

Of the various new sources of nutrients, especially proteins, microbial biomass shows great potential. This applies particularly to yeasts which have a long tradition of successful use as foods, as producers of foods and beverages, and as food ingredients (1,2,3,4,5). The interest in and the supply of yeast and microbial biomass will increase rapidly with the growing activities in biomass conversion (alcohol production, etc.). Microbial biomass can become a significant source of food protein... 

Microbial Expression of the 14-1 cDNA Encoded Polyphenolic Protein. Following transformation of a haploid yeast strain with the YpGX285 expression vector, initial studies were performed at the shake-flask level to determine whether polyphenolic protein was produced by the yeast cells upon galactose induction. Those studies demonstrated that the cells were producing the polyphenolic protein derivative and that the product was homogeneous and of the expected molecular weight. 

Conversion of the Microbially Produced Preadhesive to an Adhesive Protein. The polyphenolic protein purified from yeast adheres to a wide variety of surfaces including glass and plastic. The adherence probably results from the presence of many polar residues capable of hydrogen bonding and lysine residues that can form ionic interactions. However, this protein does not generate water-resistant bonds to surfaces nor does it have cohesive strength. For those purposes, it is necessary to convert at least a portion of the tyrosine residues to dopa and permit crosslink formation to occur after surface adhesion is achieved. That is, it is necessary to mimic the natural mussel process in which the dopa form of the polyphenolic protein is applied and then rapidly... 

Microbial processing by direct fermentation of primary biomass derivatives such as glucose can be used to synthesize a large number of organic chemicals. The cellular components that facilitate these processes are enzymes, the protein catalysts produced by the microorganisms. Some examples of direct fermenta-... 

Further processing. This may include physical or chemical treatments to modify the product. For example polysaccharides may be further fractionated to produce material of a narrow molecular size specification. They may then be activated and conjugated to carrier proteins to produce glyco-conjugate vaccines. Further purification may then be required to eliminate unwanted reactants and by-products. These processes must be done under conditions that minimize extraneous microbial contamination. If sterility is not... 

The challenge is to purify microbially produced protein-based polymers to adequate levels for use as biomaterials. The pharmaceutical use of microbially prepared insulin requires that impurities be less than 10 parts per million (ppm). Repeated use of the phase separation property for purification results in a... 

Biocompatibility of Microbially Produced Protein-based Polymers... 

Microbial digestion continues in the large intestine of ruminants volatile fatty acids and microbial protein are produced, but the protein cannot be subsequently digested and absorbed by the host animal. 

Degradability will be affected by such factors as the surface area available for microbial attack and the protective action of other constituents as well as the physical and chemical nature of the protein. Claims have been made that the solubility of a protein is correlated with ease of breakdown, but these do not survive critical examination. Thus, casein, which is readily degraded in the rumen, is not readily soluble whereas albumin, which is resistant to breakdown, is readily soluble. It has been suggested that a major factor affecting degradability is the amino acid sequence within the protein molecule. If this is so, then the nature of the microbially produced rumen peptidases is of considerable importance and it seems doubtful whether any simple laboratory test for degradability is possible. 

Convenient purification of microbially produced transductional protein-based polymers, e.g. poly(GVG T), from the cell lysate is based on a methodologv w hich utilizes the fundamental inverse temperature transitional properties (Urry et al., 1995b McPherson et al, 1996). First the bacterial cells are separated from the growth medium either by centrifugation or filtration and resuspened in Tris-HCl buffer, 50 mM, pH 8.0. Then the cells are lysed by ultrasonic disruption or French press to release the cell contents. The cell lysate is cooled to 4 C and centrifuged at high speed (10,000 x g) to remove the cold insoluble materials. The supernatant... 

Bartnicki, D., P. Lavrik, R. Leimgruber, et al. 1993. Equivalence of Microbially-Produced and Plant-Produced B.t.t. Protein also Called Colorado Potato Beetle Active Protein from Bacillus thuringiensis subsp. tenebrionis Lab Project No. 92-01-37-07 93-081E 12897. Unpublished study prepared by Monsanto Co. 95 p. 

Meeusen, R. and I. Mettler. 1994. Equivalence of Plant and Microbially Produced Bacillus thuringiensis kurstaki HD-1 Protein Lab Project Number 1/NK5EQ. Unpublished study prepared by Nothrup King Co. University of Wisconsin and Kendrick Labs. 43 p. 

Collins, M. 1996. Transgenic Maize Leaf Tissue and Microbially Produced CrylA(c) Protein Chronic Toxicity To Collembola Folsomia Candida), Under Static Conditions Lab Project Number DGC-95-A16 13601.1195.6101.123 96-3-6408. Unpublished study prepared by DEKALB Genetics Corp. and Springborn Laboratories, Inc. (SLI). 141 p. 

Therapeutics. Therapeutic materials represent a class of polypeptides that are a low volume, high value product. The production system need not be very efficient but the quaHty of the recombinant protein has to be extremely pure (33,34). Thus high cost mammalian production systems can be tolerated. However, some of the therapeutic proteins such as insulin, human growth hormone, interleukins, interferon, and streptokinase are produced microbially. 

Another microbial polysaccharide-based emulsifier is Hposan, produced by the yeast Candida lipolytica when grown on hydrocarbons (223). Liposan is apparentiy induced by certain water-immiscible hydrocarbons. It is composed of approximately 83% polysaccharide and 17% protein (224). The polysaccharide portion consists of D-glucose, D-galactose, 2-amino-2-deoxy-D-galactose, and D-galacturonic acid. The presence of fatty acyl groups has not been demonstrated the protein portion may confer some hydrophobic properties on the complex. 

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