First Generation Bioethanol Production

First generation bioethanol and biodiesel production, which mainly makes use of cereal grains and vegetable oils, represents a growing source of high quantities of protein as a valuable by-product. Sanders et al. (2007) estimated that a 10% substitution of fossil transportation fuels worldwide by first generation biofuels would result in an annual production of 100 million tonnes of protein - about four times the proteins requirement of the world s human population. A direct result of this would be the saturation of traditional protein markets. New opportunities would therefore emerge for chemical production from proteins. 

Plant Raw Materials for Use in First-generation Bioethanol Production... 

Saccharomyces cerevisiae is the dominant microorganism in the first generation of fuel ethanol production. In recent years, the worldwide bioethanol production reached around 80 billion liters per year. In a typical industrial scale bioethanol fermentation process using Saccharomyces cerevisiae, around 8-14% (v/v) ethanol is produced and the glucose to bioethanol yield is usually over 90% of the theoretical yield. In some processes, simultaneous saccharification and fermentation is applied, in which a-amylase/glucoa-mylase is mixed with Saccharomyces cerevisiae and starchy raw materials. Most of yeast cells harvested in the fermentation are recycled and sent back in order to enhance the cell concentration in the fermenter. Around 5-10% yeast cells end up in Dried Distillers Grains with Solubles (DDGS), which could be sold as animal feed. 

Figure 6.1 Schematic diagram of a typical first generation bioethanol production process.

Currently, in the first generation of bioethanol, food crops such as com, sugar cane, and wheat are used for the production of energy. These are starch- or sucrose-rich feedstocks that are readily fermented by microorganisms. However, these crops are also used for food and feed production, resulting in competition. At present, commercial production of the first-generation biomass utilizes readily-available sugars from these food plants for the fermentation process of biofuel production. 

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