Genetic Modifications of Saccharomyces cerevisiae for Ethanol Production from Starch Fermentation: A Review

Abstract

There is a huge demand for developing new technologies for alternative energy sources due to the elevated costs of petroleum and its by-products, depletion of nonrenewable fuel sources, and to eliminate the disadvantages of geopolitical location and environmental pollution caused by high levels of carbon dioxide release. Science is striving to meet this demand and as molecular biology techniques have progressed, genetic engineering tools have been presented as promising future solutions in the form of optimizing the fermentation process to increase the ethanol yield from different carbon sources such as starch. As Saccharomyces cerevisiae is not naturally able to ferment starch, it can be genetically manipulated and modulated to improve the fuel production from starchy materials and the amount of cost that is required to produce ethanol would be decreased with these manipulations. General modifications in S. cerevisiae include specific gene expressions to gain new properties or improve existing pathways. This review aims to elicit the current status of ethanol production thorough alternative techniques from starch using current genetic engineering applications and to give further directions for high-throughput fermentations using genetically modified S. cerevisiae strains.

Production of bioethanol from sago hampas via Simultaneous Saccharification and Fermentation (SSF)

“…Enzymatic saccharification is an important step prior to fermentation in yielding as much fermentation sugars as possible for the microbial conversion into ethanol. In this process, amylolytic enzymes, α-amylase and glucoamylase were used as both α-1,4 and α-1,6debranching hydrolases efficiently break down gelatinized starch into maltose and glucose, for posterior saccharification and fermentation processes (Aydemir et al 2014). These amylolytic enzymes act synergistically during the successive enzymatic saccharification of starch in accordance to several previously reported studies (Kannan et al 2013;Diong et al 2016).…”

Global Warming Potential of Biomass-to-Ethanol: Review and Sensitivity Analysis through a Case Study

“…Figure 6 shows the influence of future productivity improvements due to genetic modifications [45][46][47][48][49]. Results obtained under Simapro software analysis using the TRACI method were similar to the ones obtained previously [24], no biogenic, no land use, no allocation and cradle-to-gate borders with no transportation.…”

“…Results obtained under Simapro software analysis using the TRACI method were similar to the ones obtained previously [24], no biogenic, no land use, no allocation and cradle-to-gate borders with no transportation. Figure 6 shows the influence of future productivity improvements due to genetic modifications [45][46][47][48][49]. Results obtained under Simapro software analysis using the TRACI method were similar to the ones obtained previously [24], no biogenic, no land use, no allocation and cradle-to-gate borders with no transportation.…”

Metabolic Engineering of Oleaginous Yeasts for Production of Fuels and Chemicals

“…Starch consists of glucose monomers joined by glycosidic bonds ( Figure 3 ). The use of starch as the substrate has already been demonstrated in S. cerevisiae ( Aydemir et al, 2014 ). Recently, a Y. lipolytica strain was engineered to consume starch by expressing and secreting rice α-amylase and Aspergillus niger glucoamylase ( Ledesma-Amaro et al, 2015 ).…”