Enzymatic hydrolysis of food waste and ethanol fermentation

Abstract

SUMMARYAlthough food waste (FW) can serve as a valuable substrate containing large amounts of organic materials such as soluble sugar, starch, and cellulose, it is recognized as an environmental pollutant, and the hydrolysis of solids in FW still serves as a rate-limiting step in its biological processes. To evaluate a new potential application of FW as an alternative substrate for ethanol production through laboratory experiments, we investigated FW hydrolysis by using individual commercial enzymes and their mixtures; batch ethanol fermentation by Saccharomyces cerevisiae; and the effect of salt, which is inherently included in FW, on ethanol fermentation. A comparison of the glucose yields of the FW broth pretreated with amyloglucosidase, carbohydrase, and a mixture of both enzymes revealed that a higher glucose yield was obtained when the enzyme mixture was used (0.46 g g À1 of dry FW) than when amyloglucosidase (0.41) or carbohydrases (0.35) were used at 3 h from the initiation of the reaction. A high ethanol yield (0.23 g g À1 of dry FW) was obtained after 15 h of fermentation by S. cerevisiae by using the FW broth hydrolyzed by the enzyme mixture and was estimated to be nearly equivalent to the ethanol yields of lignocellulose biomasses. With regard to the effect of salt on ethanol fermentation, no alteration in the fermentation parameters was observed up to a salt content of 3% w/v. At a salt content of over 4%, however, substrate uptake and cell growth dramatically decreased, and a slight reduction in ethanol yield was observed. FW utilization for ethanol production by enzymatic hydrolysis and ethanol fermentation by S. cerevisiae suggests a promising practical approach to prevent environmental pollution and obtain a product of high value, ethanol.

Ethanol Production from Enzymatically Treated Dried Food Waste Using Enzymes Produced On-Site

“…On the other hand, similar results (23.3 g/L) were obtained by Cekmecelioglu and Uncu [22] with the application of a mixture of commercial cellulases and amylases. Some other research works reported higher ethanol concentration, like the one of Moon et al [10] where 29.1 g/L was produced. On the other hand, in many works, the food waste used is rich in starch which is more hydrolysable compared to cellulose (which was the main insoluble carbohydrate of the food wastes used during this work).…”

“…The disposal of large amounts of such waste can be a challenge, and cause severe environmental issues when used in landfill sites-such as uncontrolled gas emissions that contribute to the greenhouse effect, and contamination of water underground [10,11]. It has been estimated that approximately 125 m 3 of gas is produced from each ton of food waste that is used for landfill, with an average composition of 60%-65% methane and 35%-40% CO2, which is responsible for 8% of the total anthropogenic methane emissions [12].…”

“…These good yields have resulted in the construction and operation of biogas plants, which make use of food waste as raw material, either alone or in combination with other wastes such as municipal wastewater. During the last years, there has also been increased interest in exploitation of food waste for the production of ethanol [10,15,21,22].…”

Utilization Of Household Food Waste For The Production Of Ethanol At High Dry Material Content

“…This way, increasing pubic concerns about utilizing food sources for the production of biofuels can be solved, as the utilization of either sugars or corn for the production of biofuels have contributed to the increase of their price worldwide, resulting in severe problems for the poorer countries. All these concerns led to a rapid increase in research to utilize low-cost by-products and wastes as raw material [3][4][5][6]. Lignocellulosic biomass represents great potential to be utilized as raw material due to the high amounts produced every year [7], and can be derived from woody or agricultural residues such as wheat straw, corn cobs, bagasse, rice straw, et cetera.…”

“…A common practice of HFW management is landfill disposal, which is causing severe environmental problems (such as greenhouse gas emissions) and shortage of disposal places [6,12,13]. Other practices are utilization as animal feed (which can raise hygiene issues) and soil conditioners-fertilizers (which can cause severe pollution to surface and underground water) [6,12,14]. Alternatively HFW can be used for the production of bio-based (green) chemicals and bio-energy (for example, biogas and ethanol) [15,16].…”