Microorganisms have been utilized for centuries for producing food items and beverages. This article focuses on the methods for microbiological production of alcoholic beverages and their upgradation over the recent years. Micro-organisms tend to follow a standard growth curve which is utilized in the industrial applications and production of alcoholic beverages. The growth curve consists of three phases; lag, log and a saturation phase which is achieved when all the nutrients have been consumed.
However, the media composition for each phase needs to be maintained in terms of antibiotic dosing which mainly consists of penicillin and virgiolamycin. Virgiolamycin has been proven to be more effective for all the phases of the growth curve of microbes. Penicillin has a very low effect in the log, the exponential phase and no effect at all in the rest of the two phases. A summarized table is shown below to help you gain the understanding.
Microbes basically break down sugar molecules to produce alcohol or lactic acid. Microorganisms take advantage of the carbohydrates which is present in the raw materials that are used as substrate and derives energy from it for their own growth and development of the simultaneously occurring metabolic reactions. The microorganisms involved largely in alcoholic fermentation of molasses are yeast species of Saccharomyces, Torulopsis, Kloekera, Candida, and also, some particular Mucor and bacteria species. However, the most utilized microbes in industrial practices are the yeast species; especially Saccharomyces species.
Alcohol Production by Yeast
Until the research works on new techniques to produce alcohol started, the only way to produce alcohol was to ferment sugars by yeast. The main sugar sources that yeast uses can come from a various natural products; for example: grapes for wine, barley for beer, to alcohol and carbon dioxide. For the fermentation to occur, both wild and engineered strains can be used, depending upon the purpose and scale of the production.
The basic mechanism involves the reactions where the breakdown of glucose takes place in order to yield carbon dioxide and ethanol. From here on, the glucose is converted to pyruvic acid and the pyruvic may be converted into a number of products like ethanol, lactic acid etc. This old-school method is still used to produce beverages for human purposes.
However, living cells are able to contain only a certain amount of alcohol and lactic acid hence the yeast cells start dying when the concentration of alcohol goes upto 12%, in the media where the fermentation of sugars is taking place. This is basically why wines and other beverages contain only 12% of alcohol.
A Brief on the pathways : The fermentation can occur in many ways; the major fermentation pathways include Alcohol fermentation in which ethanol and CO2 are produced utilizing yeast like the Saccharomyces species; Homolactic fermentation which is the most simple pathway and it involves reactions where pyruvate goes directly to lactic acid utilizing Lactobacillus, Streptococcus, Bacillus etc; Mixed acids fermentation in which the characteristics are tested for, using the methyl red test, by utilizing E. coli; Anaerobic butyric-butyric fermentation in which the organic solvents are produced including butanol and butyric acid, by utilizing Clostridium species; Propionic acid fermentation utilizing Propionibacterium species; Butanediol fermentation in which acetoin, a precursor for butanediol, is produced which further leads to alcohol production, by utilizing Enterobacter aerogenes; Heterolactic fermentation in which ethanol, CO2, and lactic acid are produced directly, by utilizing Leuconostoc and Lactobacillus species.
Hence, in layman terms, ethanol production by fermentation is a biological-conversion process in which sugars like glucose, fructose, and sucrose are converted into cellular energy by a series of break-down reactions, leading to the production of ethanol and CO2 as metabolic waste products.
Upgradation of the methods
Over the past few decades, the researchers have been able to come up with new methods to produce alcoholic beverages. In a research conducted by Colin VL, Rodríguez A, Cristóbal HA et al. (published in J. Biomed. Biotechnol. ; 2011), a new and redesigned pathway has been developed, keeping in mind the decreasing fuel supplies, the increasing demands and the sudden unexpected climate changes. In this research, they mainly worked towards producing biodiesel through utilization of microbial systems that have been marked as a turning point in the production of biofuels. The image given below shows the redesigned pathways developed by Colin VL, Rodríguez A et al. ( NOTE: The image source is openi.nlm.nih.gov and the credits go to the respective researcher as mentioned above.)
In addition to this, the two major breakthroughs include the fermentation of sugars by corn and lignocellulose. To get a basic understanding of the two methods, one may have a look at the figure given below.
In the corn method, the sugars are broken down by amylase, an enzyme, by providing energy in the form of heat. Yeast takes the hold of the pathway from there and ferments the sugar breakdown products to form a protein named Distill. Distill is a by-product in the reaction process. Ultimately, ethanol is produced as a result of fermentation by yeast; the by-products can be filtered out or removed, later. On the other hand, in the lignocellulose method, enzymes like hemicellulase and/or cellulose are utilized to break down the sugars. The rest of the process goes on the same as the corn method.
The only difference in both the methods is that each of them uses a different energy source and catalytic enzymes. Both the methods have been proved to be working effectively and hence has increased thee opportunities for further development in the strategies to develop novel methods of alcoholic beverages' production. Hence we can conclude that over the past decades, new strategies for alcoholic beverages' production have been effectively developed and with the current research going on, it can be ensured that the finest methods are going to be in markets soon; marked healthy and in accordance with the ethical and the constantly decreasing fuel sources issues.
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