Value-Added Products from Ethanol Fermentation—A Review

Abstract

Global demand for renewable and sustainable energy is increasing, and one of the most common biofuels is ethanol. Most ethanol is produced by Saccharomyces cerevisiae (yeast) fermentation of either crops rich in sucrose (e.g., sugar cane and sugar beet) or starch-rich crops (e.g., corn and starchy grains). Ethanol produced from these sources is termed a first-generation biofuel. Yeast fermentation can yield a range of additional valuable co-products that accumulate during primary fermentation (e.g., protein concentrates, water soluble metabolites, fusel alcohols, and industrial enzymes). Distillers’ solubles is a liquid co-product that can be used in animal feed or as a resource for recovery of valuable materials. In some processes it is preferred that this fraction is modified by a second fermentation with another fermentation organism (e.g., lactic acid bacteria). Such two stage fermentations can produce valuable compounds, such as 1,3-propanediol, organic acids, and bacteriocins. The use of lactic acid bacteria can also lead to the aggregation of stillage proteins and enable protein aggregation into concentrates. Once concentrated, the protein has utility as a high-protein feed ingredient. After separation of protein concentrates the remaining solution is a potential source of several known small molecules. The purpose of this review is to provide policy makers, bioethanol producers, and researchers insight into additional added-value products that can be recovered from ethanol beers. Novel products may be isolated during or after distillation. The ability to isolate and purify these compounds can provide substantial additional revenue for biofuel manufacturers through the development of marketable co-products.

Mass Specthoscope: A Hand-held Extendable Probe for Localized Noninvasive Sampling of Skin Volatome for Online Analysis

“…VOCs can be formed in meat in the course of Maillard reaction, alcoholic fermentation, , microbial activity, and lipid oxidation . The presence of acetic acid, ethyl acetate, and butanol is attributed to microbial activity during ham spoilage .…”

“…We observed that the intensities of ethanol and acetone were higher in the spoiled ham than in the fresh and semispoiled ham (Figure ). The ethanol production in ham can be associated with alcoholic fermentation, indicating the occurrence of microorganisms such as yeast or bacteria, which enzymatically convert sugars present in ham into ethanol. , On the other hand, acetone may indicate the occurrence of early-stage degradation of muscle glycogen . The following VOCs were also found in the semispoiled and spoiled ham samples: ethylene ( m / z 29.0386), acetic acid ( m / z 61.0284), butanol ( m / z 75.0804), and eugenol ( m / z 165.0910).…”

Beyond Bread and Beer: Value-Added Products from Wheat

“…Fermentation using yeast (typically Saccharomyces cerevisiae) converts the sugar to ethanol, with many factors affecting the final ethanol yield [113]. After fermentation, the mixture, called beer, is transferred to a distillation system where ethanol is distilled from the beer [13]. Finally, the ethanol mixture is further purified through rectification and dehydration, resulting in a final ethanol concentration of 95% or higher [114].…”

“…During fermentation of wheat grain, additional value-added compounds are also produced including glycerol, succinic acid, acetic acid, lactic acid, and α-glycerylphosphorylcholine (e.g., a nootropic compound) [13,118]. The nootropic compound α-GPC has been investigated as a treatment for Alzheimer's disease and strokes [119].…”

“…Wheat bioethanol is a renewable source of fuel, and its use can reduce greenhouse gas emissions when used to displace petroleum-based gasoline. Several valuable co-products can also arise from ethanol fermentation, including nootropic compounds, organic acids, glycerol, and a variety of fusel alcohols [13].…”