Fermentative microorganisms

The yeasts used in the production of mead are usually strains of Saccharo-myces cerevisiae, similar to that used in wine, beer, and champagne productions. These yeasts metabolize sugars, such as glucose and fructose, resulting in the formation of ethanol and carbon dioxide. Nevertheless, the yeast Hansenula anomala had also given good results (Qureshi and Tamhane, 1987). 

Strains of S. cerevisiae used include Cll-3 (Navratil et al., 2001), BRL-7 (Qureshi and Tamhane, 1986), and UCD522 (Mendes-Ferreira et al., 2010) from culture collections, as well as commercial strains, such as Premier cru (Pereira et al., 2009) and ENSIS-LE5 (Roldan et al., 2011). 

Nevertheless, honey and wine musts have different compositions in regard with sugar content (nearly 3 times higher in the former) and nitrogen concentrations (about 100 times higher in the last). Thus, wine 

Seven S. cerevisiae strains were characterized relative to their resistance to sulfur dioxide (since it is a desirable feature in the fermentative yeast strains), ethanol (where tolerance is an indispensable property due to the high concentrations reached by the end of fermentation (Carrasco et al., 2001)), and osmotic stress (due to the high osmotic potential of mead at the commencement of fermentation). Pereira (2008) and Pereira et al. (2009) verified that significant differences did not exist between the strains. S. cerevisiae strains isolated from honey were similar to commercial and reference strains—all appearing to be suitable for mead production. 

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In environments lacking a suitable external electron acceptor - such as dioxygen, sulfate, or ferric iron - respiration is not possible. Here, many organic compounds may be metabolized by fermenting microorganisms. Microbes of this class may create ATP by a direct coupling mechanism, using a process known as substrate level phosphorylation, SLP with an ion translocation mechanism like that employed by respirers, as already described or by a combination of SLP and ion translocation.1... 

The fungi (e.g., molds, mildews, rusts, yeasts, or mushrooms) are the third major group of solid phase microorganisms. However, they differ from bacteria and actinomycetes in that they are eukaryotic. They are all heterotrophic, and most are aerobic, with the exception of yeasts, which are fermenting microorganisms. 

There has been considerable research over the past 5-10 yr dedicated to improving microorganisms and separations technologies in order to reduce the overall cost of biobased succinic acid, much of which has been cofunded by DOE. This research has resulted in the development of the fermentation microorganism Escherichia coli strain AFP111, which exhibits greatly improved productivity. Fermentation with AFP111 to produce succinic acid has recently been successfully tested at commercial scale. 

This chapter presents a comprehensive review of previous research on mead production. It will focus on honey characterization and mead production. The first section covers honey composition and the way this affects honey properties, as well as important parameters that are indicators of honey quality. The second section discusses mead production, including fermentative microorganisms, fermentation conditions, and required postfermentation adjustments and maturation conditions. The final section focuses on the problems that must be surpassed and what the future holds for mead production. 

II. Mead production—under this heading are discussed fermentative microorganisms, fermentation conditions, postfermentation adjustments, and maturation conditions. 

Fermentation [16]. Some important pharmaceuticals, including steroids, antibiotics, and certain food additives (such as vitamins) are produced by fermentation. In fermentation, microorganisms (e.g., bacteria, yeast, or fungi) are inoculated in a liquid broth supplemented with nutrients (e.g., temperature, pH, oxygen). These microorganisms produce the desired product (e.g., antibiotic, steroid, vitamin, and so on) as a by-product of normal metabolism. The process of fermentation includes three steps ... 

Although we have considered only lactic acid and alcoholic fermentation, microorganisms are capable of generating a wide array of molecules as end... 

To make natto, soybeans, preferably small seeded, are washed and soaked overnight. The soaked beans are then steamed for 30 min, drained, and cooled to -40°C. Traditionally, the treated soybeans are wrapped with rice straw and set in a warm place for 1-2 days. Rice straw is credited for not only supplying the fermenting microorganism, Bacillus natto, but also absorbing the unpleasant odor of ammonia released from natto and imparting the aroma of straw to the product. 

McFeeters, R.F., Fermentation microorganisms and flavor changes in fermented foods, J. Food Sci., 69, 35, 2004. 

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