Publisher Summary This chapter provides a comprehensive survey of diol production, including biochemistry, microbiology, and process engineering Two microbial species have demonstrated a potential for diol production on a commercial scale Klebsiella pneumoniae, with broad substrate and environmental adaptability, is the most thoroughly investigated organism The ability to utilize starchy feedstocks is the main advantage of Bacillus polymya Utilization of “waste” cellulosic substrates is generally recommended for improvement of process economics Efficient conversion of hemicellulosic carbohydrates is thus essential The optimal conditions for bioconversion of glucose are clearly distinct from those for xylose This is especially true in terms of culture pH and aeration and to a lesser extent in temperature and nutrient supplementation The most effective process designs may permit separate conditions for the consumption of these sugars In a batch operation, this could be accomplished through a midrun adjustment of key environmental parameters In continuous production, separate reactors could be operated in a series with residence times and conditions established for optimal consumption of the glucose and xylose Recovery of butanediol from fermented broths is especially difficult due to the physical and chemical properties of the compound Solvent extraction and steam stripping appear to be the most effective alternatives at present Incentives to seek renewable alternatives to petroleum-based fuels and chemicals in combination with advances in microbial process efficiency may yet result in an economically viable system for the production of butanediol from biomass resources

The Microbial Production of 2,3-Butanediol

Biosynthesis of Flavor Compounds by Microorganisms

Tracking spore-forming bacteria in food: From natural biodiversity to selection by processes

The preservative benefits of the enzymic glucose oxidase/catalase system were measured in refrigerated, fresh, whole winter flounder (Pseudopleuronectes americanus Waldbaum) and winter flounder fillets. The enzyme system was applied as a dip, as an ice and immobilized in algin blankets. Advantages were an extended period of sensory acceptance and delayed onset of putrefactive odors, 21 days vs 15 days for controls. The pattern of endogenous hypoxanthine accumulation and decline was unaffected, but parameters thought to measure proteolytic activity were modified: creatinine turnover was slowed and ammonia generation was retarded.

Utilization of Glucose Oxidase for Extending the Shelf-Life of Fish

Recognition of greater diversity of Bacillus species and related bacteria in human faeces.

Publisher Summary Food quality is largely the sum of the characteristics, which register favorably or adversely on an individual's senses. These characteristics include freshness, flavor, odor, texture, tenderness, consistency, color, size and shape, degree of ripeness, and presence or absence of defects. Nutritive value, chemical residues, and disease-producing organisms are also a part of food quality, although these are not measured by the senses of smell, taste, sight, or touch. When one visualizes a spectrum ranging from good to poor quality, the extremes are easily differentiated. This is not true for the central part of the spectrum, however, especially for products in which the manufacturing process tends to mask differences, as with comminuted foods. When foods become more abundant, standards of quality are likely to be higher and more clearly defined. Quality, which is acceptable in one society may not be in another. Chemical indicators may be the only means of evaluating quality in some foods, as processing methods, such as filtration, preclude the use of conventional methods, such as plate counts. In some foods, indicator compounds may supplement microbiological methods of analyzing food quality, including plate counts, mold counts, rot fragment counts, and direct microscopic counts. The use of chemical indicators assists the manufacturer in producing and maintaining high-quality foods. This chapter discusses the background dominant spoilage flora, and chemical indicators of microbial spoilage of: chemical indicators of quality for foods with high protein content, chemical indicators of quality for foods with high fat content, and chemical indicators of quality for foods with high carbohydrate content.

Food quality as determined by metabolic by-products of microorganisms.

Samples of sugar, starch, spices, and miscellaneous products were tested for thermophilic sporeformers of Bacillus to determine the dominant species present. Surface colonies selected at random were identified. Six species of Bacillus were isolated: B. stearothermophilus, B. coagulans, B. licheniformis, B. subtilis, B. circulans, and B. pumilus. Samples of starch and pepper were tested for thermophilic sporeformers of Bacillus to determine the distribution of rough and smooth variants. Colonies were classified as rough or smooth variants by colonial characteristics. The distribution of variant forms in these two products was significantly different. Starch samples showed predominantly rough variants; pepper samples showed predominantly smooth variants.

Distribution of thermophilic aerobic sporeforming bacteria in food ingredients.

Rhizopus nigricans and Penicillium expansum produced 2,3-butylene glycol which accumulated in natural and artificial media with time. Mycelial mats of P. expansum decreased the quantity of a diacetyl substrate and converted part of this substrate into acetylmethylcarbinol (AMC) and 2,3-butylene glycol. Mycelial mats of P. expansum also decreased AMC substrate with the formation of 2,3-butylene glycol. 2,3-Butylene glycol decreased slightly during incubation with the fungal mat. The formation of AMC was suppressed significantly by cysteine and ascorbic acid.

Bonnie S. Richmond

Papers

Food quality as determined by metabolic by-products of microorganisms.

Distribution of thermophilic aerobic sporeforming bacteria in food ingredients.

Substrate Effect on 2,3-Butylene Glycol Production by Rhizopus nigricans and Penicillium expansum