Proteins - continued microbial

When sufficiently high levels of expression and protein accumulation are achieved, efficient downstream processing protocols must be developed to insure product quality and the economic feasibility of production. As the demand for safe, recombinant pharmaceutical proteins continues to expand, the market potential of plant-produced recombinant proteins is considerable. Molecular farming can produce recombinant proteins at a lower cost than traditional expression systems based on microbial or animal cell culture, and without the risk of contamination with human pathogens. 

Animal Nutrition. Sulfur in the diets of mminant animals is beneficial to the animals growth (see Eeedsand FEED ADDITIVES). Sulfur increases feed intake, cellulose and dry matter digestion, and the synthesis of microbial protein. This results in increased meat, milk, and wool production (43). The special uses for sulfur in agriculture demonstrate a significant and continuing need for increased use of sulfur (44). 

In biochemical engineering processes, measurement of dissolved oxygen (DO) is essential. The production of SCP may reach a steady-state condition by keeping the DO level constant, while the viable protein is continuously harvested. The concentration of protein is proportional to oxygen uptake rate. Control of DO would lead us to achieve steady SCP production. Variation of DO may affect retention time and other process variables such as substrate and product concentrations, retention time, dilution rate and aeration rate. Microbial activities are monitored by the oxygen uptake rate from the supplied ah or oxygen. 

In general, biomolecules such as proteins and enzymes display sophisticated recognition abilities but their commercial viability is often hampered by their fragile structure and lack of long term stability under processing conditions [69]. These problems can be partially overcome by immobilization of the biomolecules on various supports, which provide enhanced stability, repetitive and continuous use, potential modulation of catalytic properties, and prevention of microbial contaminations. Sol-gel and synthetic polymer-based routes for biomolecule encapsulation have been studied extensively and are now well established [70-72]. Current research is also concerned with improving the stability of the immobilized biomolecules, notably enzymes, to increase the scope for exploitation in various... 

Kuehler and Stine (43) studied the functional properties of whey protein with respect to emulsifying capacity as affected by treatment with three proteolytic enzymes. Two microbial proteases and pepsin were examined. The emulsion capacity decreased as proteolysis continued, suggesting that there is an optimum mean molecular size of the whey proteins contributing to emulsification. 

Whey permeate may also be fermented anaerobically to fuel gas. Studies have also been reported on the production of ammonium lactate by continuous fermentation of deproteinized whey to lactic acid followed by neutralization with ammonia. Conversion of whey and whey permeate to oil and single-cell protein with strains of Candida curvata and Trichosporon cutaneum have been examined. Production of the solvents n-butanol and acetone by Clostridium acetobutylicum or C. butyricum is under investigation in New Zealand. Whey permeate also has potential for citric acid and acrylic acid manufacture. Extracellular microbial polysaccharide production from whey permeate has... 

The sol-gel procedure enables encapsulation of enzymes in optically transparent, porous silicate matrices, under mild room-temperature conditions. The small pores prevent microbial degradation and, due to the biomolecule size, they will not diffuse out of the polymer network. The physical encapsulation avoids self-aggregation effects as well as protein unfolding and denaturalization. At the same time, the catalytic activity is maintained as the enzymes are able to react with small substrates that can transfer across or within the support, assuring continuous transformations [75]. 

The area covered by natural products chemistry is boundless as it deals with nature itself. There is literally no limit to the topics to be dealt with. This volume 29 continues the tradition of supplying us with superb review articles written by experts. The articles in this volume deal with the screening, isolation, structure, synthesis, biosynthesis, and pharmacology of plant and microbial natural products that exhibit antimitotic, cancer chemotherapeutic, enzyme inhibitory, antiinflammatory, antibiotic and molting hormone activities. The compound types also cover a huge range of natural products, i.e., polyketides, terpenoids, sugars, alkaloids, proteins, and enzymes. 

People in many regions of the world suffer from protein-calorie malnutrition. If the world population continues to expand toward seven billion by the 21st century the need for more protein will become accentuated. As real demand for protein increases with a burgeoning population and as the emphasis changes from conventional agriculture (because of limitations of land and energy) to more direct consumption of plant and microbial proteins the necessity for new processes and new products will increase. 

Another significant problem associated with consumption of microbial cells is their high content of nucleic acid (NA) which ranges from 8 to 25 gms nucleic acid per 100 gms protein and most of the nucleic acid is present as RNA (55). Before single-cell protein can be used as a major source of protein for human consumption, the content of nucleic acid has to be reduced, so that the daily intake of nucleic acid from yeast would not exceed 2 gms (i.e. 20g yeast). Higher quantities cause uricemia and continued ingestion of SCP may result in gout (56,57). 

Furthermore, esters of tylosin such as AIV (14) inhibited protein synthesis and bound to tylosin-resistant ribosomes [77], These results illustrate the dynamics of microbial resistance as antibiotics are developed to combat microorganisms which are continually evolving and acquiring new means of blocking the actions of antibiotics. 

---