## 1 Introduction  
Renewable energy attracts attention for the protection of the environment and supplies our energy needs by reducing dependence on petroleum and non-renewable energy sources. Bio-ethanol, which is one of the energy sources, is known to be a potential alternative to petroleum-derived fuels and has the potential to meet the increasing demand for energy for industrial processes, heating and transportation [1]. In 2009, 19,534.99 millions of gallon of ethanol were produced worldwide [2]. The U.S. and Brazil are the two major countries and produced 10,600.00 and 6,577.89 million gallon of ethanol in 2009, respectively [2]. However, the U.S. is still the largest petroleum consumer in the world and consumed 18.8 million barrels per day of petroleum products in 2011. Advanced bio-fuels (may include ethanol derived from cellulose, sugar or starch, or waste material, including crop residue, other vegetative waste material, animal waste, and food waste) production under The U.S. Renewable Fuel Standard (RFS) scenario could reduce U.S. petroleum import by approximately $23 billion in 2016 according to the report for \"U.S. Economic Impact of Advanced Biofuels Production: Perspectives to 2030\" [3].  
Sugar cane, as a raw material, is used for 60% of global ethanol production, however; corn is the main raw material of ethanol production in the United States (90%) [1]. These carbon sources are high value products as a food source [4; 5]. Potato is another high value crop as a food source and currently, utilized 60% frozen, 14% fresh, 13% chip, 13% dehydrated, and 1% potato seedin the US [6]. Today, the U.S. produces about 460 billion pound of potatoes annually on 1.3 million acres with an approximate value of 3$ billion. During processing of potato, some of the potatoes wasted, for example 18% in the potato chips industry and 5%-20% in potato cultivation [7; 8] Keystone Potato Products, LLC (Hegins, PA) manufactures potato products including potato flakes with the capacity of 7,700 kg/h, out of 900 kg skin and 225 kg low quality waste mash potato per h (Personal communication with [PERSON]). Therefore, the waste from potato industry can be utilized as growth media for the fermentation processes. The wastes of potato industry are currently being utilized as animal feed [9]. However, they can be consumed for ethanol production without requiring drying process. Waste of potato industry could be an economical carbon source for ethanol fermentation in the industry, because of high starch content of potato wastes. Waste potato mash is a waste of potato flakes process and composed of approximately 80% moisture. Hydrolysis is a process of breaking down starch (amylopectin and amylose) into fermentable sugars and is needed before the fermentation. Hydrolysis is carried out at high temperature (90-110 \({}^{\circ}\)C); however, at low temperatures, it is possible and can contribute to energy savings [10]. To convert starch into the fermentable sugars, either acid hydrolysis or enzymatic hydrolysis needs to be performed. Each has their own set of advantages and disadvantages for use. The limitations of acid hydrolysis can be by-products inhibition on growth of yeast (such as 5-hydroxymethylfurfural (5-HMF)), neutralization before fermentation and expensive constructional material due to corrosion risks [11]. On the other hand, high prices of enzymes play a crucial role when feasibility is of concern. Enzyme hydrolysis is chosen even though high cost of enzymes and initial investment because of high conversion yield of glucose [11]. Amylases (\(\alpha\)-amylase, \(\beta\)-amylase, and glucoamylase) are employed for hydrolysis of starchy materials. Although amylases are derived from plants, animals, and microorganisms, microbial amylases are in use commonly [12]. \(\alpha\)-Amylase (endo-1,4-\(\alpha\)-d-glucan glucohydrolase, EC 3.2.1.1) hydrolyses the 1,4-\(\alpha\)-d-glucosidic linkages in the linear amylase chain, randomly.