John H. Litchfield

Microbiological Production of Lactic Acid

Publisher Summary The chapter focuses on the production of lactic acid by microbiological processes. It discusses the chemical and physical properties of the acid followed by its commercial uses. Lactic acid, 2-hydroxypropanoic acid or α-hydroxypropanoic acid, is served as a food preservative in fermented milks, fruits, vegetables, meats, and breads. Various carbohydrate raw materials are used for lactic acid production by bacteria and molds such as refined carbohydrate raw materials; glucose, sucrose, and starch; complex carbohydrates—cellulose, cereal grains, corn, Jerusalem artichokes, and potatoes; and waste materials—cheese whey and permeate, municipal solid waste, and wood molasses. Factors affecting lactic acid concentrations, productivities, and yields include types of process (batch, fed-batch, or continuous), microorganism, strain, inoculum size and nutritional state, temperature, pH, substrate concentration and pretreatment, the presence of competing contaminants in non sterile systems, the presence of bacteriophages, and inhibition by lactic acid with increasing concentrations and by toxic products from substrate pretreatment such as furfural and hydroxymethylfurfural. The chapter also discusses various methods of product recovery and purification namely precipitation and acidification, centrifugation and microfiltration/ultrfiltration, distillation, ion exchange and adsorption, reverse osmosis, and solvent extraction and extractive fermentation. Various types of process controls are also summarized.

Single-cell proteins

Both photosynthetic and nonphotosynthetic microorganisms, grown on various carbon and energy sources, are used in fermentation processes for the production of single-cell proteins. Commercial-scale production has been limited to two algal processes, one bacterial process, and several yeast and fungal processes. High capital and operating costs and the need for extensive nutritional and toxicological assessments have limited the development and commercialization of new processes. Any increase in commercial-scale production appears to be limited to those regions of the world where low-cost carbon and energy sources are available and conventional animal feedstuff proteins, such as soybean meal or fish meal, are in short supply.

Salmonella and the food industry ‐ methods for isolation, identification and enumeration

The presence of Salmonella in foods is a continuing problem for the food industry. These organisms are frequently found in food products of animal origin. In particular, turkeys and chickens were implicated in 36% of the food‐borne outbreaks reported in 1971. This review discusses the various procedures that can be used for isolating, identifying, and enumerating Salmonella in foods and the advantages and limitations of these procedures. Some of the methods for rapid detection of salmonellae such as enrichment serology and fluorescent antibody procedures are considered. It is pointed out that at the present state of development, none of the rapid methods can be substituted completely for conventional cultural methods in isolating and identifying salmonellae in foods.

Microbial Protein Production

During the past decade, numerous processes have been developed for producing cells of microorganisms for use as protein sources in human food or animal feed. This paper will consider the raw materials and microbes suitable for producing single-cell proteins (SCP) and the factors affecting their use. The discussion will include photosynthetic and nonphotosynthetic microorganisms--algae, bacteria, actinomycetes, yeasts, molds, and higher fungi-and raw materials for growth such as hydrocarbons and petrochemicals; agricultural, industrial, and forest products; and food-processing wastes. The emphasis will be on the processes that have been operated on a pilot-plant or commercial scale.1

Microbiological and enzymatic treatments for utilizing agricultural and food processing wastes

Abstract Agricultural and food industry wastes include both solids and liquids that pose potentially severe pollution problems and are subject to increasing governmental regulations. In this presentation, emphasis is placed on microbiological and enzymatic processes for recovering animal feeds, food additives, chemicals and fuels from these wastes. Under aerobic conditions, carbohydrates, lipids and proteins in wastes can be converted by microorganisms to yield microbial biomass or single‐cell proteins to be used for animal feeds or human foods. Also, they can serve as substrates for producing chemicals or enzymes, or for enzymatic conversion to sugar syrups, fatty acids, or amino acids. Under anaerobic conditions, wastes containing carbohydrates, lipids, and proteins can be digested to yield methane. Also ethanol or organic acids can be produced from carbohydrates by anaerobic microbiological processes. Key considerations in determining the advisability of utilizing these wastes include the following: co...

Algae, bacteria, and yeasts as food or feed

The use of algae, bacteria, and yeasts as food for man or feed for animals has been the subject of considerable discussion in both the scientific and technological literature and in the popular press in recent years. This interest has arisen largely as a result of the need for additional food supplies in chronic food‐shortage areas of the world and for food for life‐support of astronauts on extended space missions. We direct out attention here to the most recent literature and attempt to analyze the current status of the use of these microorganisms for either food or feed with projections to possible applications in the future.

The lipid composition and conversion of tryptamine toNb-acetyltryptamine in aCatharanthus roseus cell line without indole alkaloids

SummaryA cell line, NA13-2, was selected as a rapidly growing colony of protoplasts from a UV(254 nm)-fluorescent cell line, NA13-1, which originated from a tryptamine-resistant strain ofCatharanthus roseus NA13. Cell line NA13-2 lost the capability to produce indole alkaloids. Tryptophan fed to these cells was converted toNb-acetyltryptamine as the major product. The free acetyl coenzyme A content of NA13-2 cells was 50% higher than in the mother cells. The total lipid content of the NA13-2 cells was 2.5-fold that in the NA13 cells. In spite of the similarity in the fatty acid content to that of the mother cell line NA13, the total lipid extract of NA13-2 cells appeared as a wax instead of an oil, resulting from the presence of sterol esters.

Functional Properties of a High Protein Beverage Stabilized with Oat-β-Glucan: Properties of a high protein beverage…

This study evaluated the effect of oat flour and milk protein on the functional properties and sensory acceptability of shelf stable high protein dairy beverages containing at least 0.75 g of oat-β-glucan per serving size. Formulations adjusted to levels of 1.50% to 2.30% oat flour and 2.50% to 4.00% milk protein isolate (MPI) were thermal processed in a rotary retort. The finished product exhibited good suspension stability (>80%). The increase of oat and MPI contents lead to nectar-like beverages (51 to 100 mPas). However, oat flour was the component showing the highest effect on the viscosity coefficient values of the beverages. Sensory evaluation indicated that formulations with less than 1.9% oat flour and 2.5% MPI (thin liquid, <50 mPas) were the most accepted. Mouthfeel (perceived thickness), sweetness and aftertaste had the most influence on overall liking of the beverages. PRACTICAL APPLICATION Overall, this study comprises the development of a functional food product. Supplementation of beverages with fiber from oats is an innovative approach to stabilize high protein beverages. Ready to drink protein beverage formulations use gums to stabilize the product and provide a desirable mouthfeel. The levels of oat-β-glucan used in the beverage increased the thickness and meet the requirement of the FDA approved health claim for reduction of the cardiovascular disease risk (21 CFR 101.81).

Engineering Requirements for Culturing of Hydrogenomonas Bacteria

Continuous culture system for Hydrogenomonas bacteria in waste management of life support system