The gene encoding neomycin phosphotransferase II (NPTII) has been used routinely as a selectable marker in the production of genetically engineered crops. To facilitate the safety assessment of this protein, the same coding sequence used for plant transformation was introduced into Escherichia coli to produce gram quantities of this protein. A unique, simple, rapid and efficient purification method was developed to purify thirty grams of NPTII protein. The microbially produced NPTII was shown to be chemically and functionally equivalent to the NPTII protein expressed in and purified from genetically engineered cotton seed, potato tubers and tomato fruit. Microbially produced and plant produced NPTII proteins have comparable molecular weights, immuno-reactivities, epitope structures, amino terminal amino acid sequences, biological activities and both lack glycosylation. Demonstrating the equivalence of NPTII protein from these sources establishes the validity of using the microbially produced NPTII to assess the safety of the NPTII protein produced in genetically engineered crops.

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Conditions to obtain correctly folded PMP-1a (promegapoietin-1a), an engineered fusion IL-3 (interleukin-3) and thrombopoietin receptor agonist from recombinant Escherichia coli IBs (inclusion bodies), were defined to generate sufficient amounts of protein for evaluation as a potential therapeutic compound. Several ionic and non-ionic detergents, as well as the chaotrope urea, in combination with selected additives, were screened for their ability to dissolve IB protein and promote formation of monomeric, oxidized protein. Upon dissolution, soluble aggregates constituted 50-60% of total protein in detergent-solubilized IBs depending on the level of detergent used, whereas use of urea increased aggregation to approx. 70%. Subsequent addition of 5 mM cysteine or DTT (dithiothreitol) reduced the levels of aggregation, but never lower than approx. 20%. Refolds from detergent-solubilized IBs with or without organic modifiers characteristically produced multiple persistent misfolded species. However, the addition of a 12:1 molar excess of cystine (cystine/DTT) to urea-dissolved IBs containing DTT, followed by dilution, promoted the formation of correctly oxidized, disulfide-paired PMP-1a monomer with minimal misfolds present. Thus treatment of urea-dissolved proteins with thiol-group-containing additives and control of dilution, pH, protein concentration and order of addition were able to produce a maximum refold efficiency of 40-50% of correctly paired protein monomer.

Gluconobacter oxydans has the unique ability to regioselectively and rapidly oxidize sorbitol and other erythro saccharides. In this report a new process is described by which N-butylglucamine is regioselectively oxidized by the organism. A large-scale process is described by which N-butylglucamine can be converted to an intermediate (6-deoxy-6-butylaminosorbose) which can be readily converted to N-butyldeoxynojirimycin by catalytic hydrogenation. The primary process variables of temperature, pH, and added acids and salts were investigated in laboratory bioreactors. Since degradation of the sorbose product was rapid above room temperature, significant enhancement of the selectivity was achieved by lowering the temperature at which the bioconversion was run. The optimum temperature for this conversion was 12−15 °C. The pH maximum of the bioconversion was 5.5−6.0. However, the small gain in rate relative to pH 5.0 was at least offset by the increase in degradation of the product at the higher pH. Nitrate salts of N-butylglucamine could replace chloride salts, but sulfate, acetate, and phosphate salts could not. Sulfate in particular led to inhibition of the conversion, while phosphate and acetate led to increased degradation. At temperatures in the range of 12−15 °C, pH of around 5.0 and substrate concentrations of 0.2 M, Gluconobacter oxydans catalyzed bioconversion to 6-deoxy-6-butylaminosorbose with yields approaching 95%. These conditions were used to scale this process to 5500-L scale.

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