1. Introduction
Ethanol is considered as one of the most promising renewable fuel that can replace fossil fuels-based transportation fuels. It is most commonly produced by microbial (most often yeast) catalyzed fermentation using plant biomass as a raw material. Starchy raw materials (i.e. corn, wheat, sorghum) are still the most common feed-stocks for fuel ethanol production in temperate climate regions of the world (Europe, North America, Central Asia). However its use as fuel production resources may affect on the prices of food products manufactured from them. The use of non-edible parts of the plant (straws, stalks), known as the lignocellulose biomass, as the raw material in distillery is nowadays considered as the most promising opportunity for ethanol production that does not affect the prices of foodstuffs. However, the conversion of lignocellusosic biomass into ferment-able sugars and, subsequently into ethanol requires high temperature pretreatment which is often catalyzed using corrosive, non-ecological or costly agents like acids, alkali, ionic liquids and others. Moreover the efficiency of saccharification and fermentation of lignocellulose is still much less efficient in comparison to starches, but starchy raw materials are very costly and the cost of the feedstock can exceed 65% of the price of final product. The solution to the problems of affecting food prices by using agricultural crops for fuel production and the technological difficulties with conversion of lignocellulosic biomass is utilization of food industry wastes for production of biofuels. One of the most promising food waste that can be processed into ethanol is waste bread. It contains significant amount of starch that is easily hydrolyzed to monomeric sugars using amylases, the amount of starch and simple sugars in bread ranges 500–750 and 3–50 g kgÀ1 respectively. Moreover bread contains 100–150 g kgÀ1
of protein which, after hydrolysis to peptides and amino acids, is essential for yeast growth and accelerated fermentation. Waste bread is also highly accessible raw material for ethanol processing. The estimated wastage for bakery products ranges 7–10% of its total production, taking into consideration estimated world annual production of bread which is about 100 million tones the amount of generated waste can reach even 10 million tones per year worldwide. The major factor for bread waste formation is that part of the produced product is left unsold and is returned to the bakery due to significant level of staling and large amount of available assortment of bakery products which are produced in excess to fulfill the consumers demands. There are limited possibilities for reprocessing bread waste in the bakeries. Some wastes can be processed into bread crumbs, as a replacement of part of flour in sourdough preparation or as animal feed. However due to often microbial spoilage its use for human and animal nutrition could be risky for health of the consumers. These problems are the reason why waste bread is most often left on landfills or used as a fuel for combustion. The most promising solution for waste bread utilization is use it as a raw material for ethanol fuel production. Earlier studies shown that waste bread is a high-yielding material for ethanol fermentation. The amount of ethanol produced from bread waste that shown no signs of mould contamination, depending on processing technology, ranged as mentioned by the authorsca. 350–370 g kgÀ1 of feedstock dry matter. Kawa-Rygielska and Pietrzak studied the possibility of using waste bread showing high level of surface mould contamination for ethanol production, this resulted in a decrease of ethanol yield in comparison to non contaminated material (ca. 230–250 g kgÀ1 depending on the raw material loading in the fermentation feed). The other possibilities for waste bread utilization via biotechnological processes are in example: solid state fermentation by Aspergillus awamori for production of amylases and proteases, biohydrogen production using rhizosphere microflora, succinic acid production by Actinobacillus succinogenes or aromatic compounds production by Geotrichum candidum.
1. บทนำ เอทานอลถือเป็นหนึ่งในเชื้อเพลิงทดแทนว่าสามารถแทนเชื้อเพลิงการขนส่งที่ใช้เชื้อเพลิงฟอสซิล มักผลิต โดยจุลินทรีย์ (มักยีสต์) กระบวนหมักใช้พืชชีวมวลเป็นวัตถุดิบ ฟูมดิบ (เช่นข้าวโพด ข้าวสาลี ข้าวฟ่าง) ยังคงมีอาหารหุ้นมากที่สุดสำหรับการผลิตเอทานอลน้ำมันในอุณหภูมิที่ภูมิภาคของโลก (ยุโรป อเมริกาเหนือ เอเชียกลาง) อย่างไรก็ตาม การใช้เป็นเชื้อเพลิงผลิตทรัพยากรอาจมีผลต่อราคาของผลิตภัณฑ์อาหารที่ผลิตจากพวกเขา การใช้-กินส่วนของพืช (หลอด stalks), เรียกว่าชีวมวล lignocellulose เป็นวัตถุดิบในโรงกลั่นสุราในปัจจุบันถือว่าเป็นโอกาสว่าสำหรับการผลิตเอทานอลที่มีผลต่อราคาของกิน อย่างไรก็ตาม การแปลงของชีวมวล lignocellusosic เป็นความสับสนอลหม่านต่อได้น้ำตาล และ ต่อมา เป็นเอทานอลต้อง pretreatment อุณหภูมิสูงซึ่งจะมักกระบวนใช้กัดกร่อน ไม่ใช่ระบบนิเวศ หรือตัวแทนเสียค่าใช้จ่ายเช่นกรด ด่าง ของเหลว ionic และอื่น ๆ นอกจากนี้ efficiency ของ saccharification และหมัก lignocellulose ได้ยังมากน้อย efficient โดยสมบัติ แต่ฟูมวัตถุดิบมีราคาแพงมาก และต้นทุนของวัตถุดิบสามารถเกิน 65% ของราคาของผลิตภัณฑ์ final การแก้ไขปัญหาส่งผลกระทบต่อราคาอาหารโดยใช้พืชทางการเกษตรสำหรับการผลิตเชื้อเพลิงและ difficulties เทคโนโลยีแปลงของชีวมวล lignocellulosic เป็นการใช้ประโยชน์ของเสียอุตสาหกรรมอาหารสำหรับการผลิตเชื้อเพลิงชีวภาพ หนึ่งเสียอาหารว่าสามารถประมวลผลลงในเอทานอลคือขนมปังเสีย มันประกอบด้วย significant จำนวนแป้งที่ง่าย ๆ hydrolyzed กับน้ำตาล monomeric ใช้ amylases แป้งและน้ำตาลอย่างง่ายในขนมปังช่วง 500 – 750 และ kgÀ1 3 – 50 กรัมตามลำดับ นอกจากนี้ ขนมปังประกอบด้วย kgÀ1 100 – 150 กรัมof protein which, after hydrolysis to peptides and amino acids, is essential for yeast growth and accelerated fermentation. Waste bread is also highly accessible raw material for ethanol processing. The estimated wastage for bakery products ranges 7–10% of its total production, taking into consideration estimated world annual production of bread which is about 100 million tones the amount of generated waste can reach even 10 million tones per year worldwide. The major factor for bread waste formation is that part of the produced product is left unsold and is returned to the bakery due to significant level of staling and large amount of available assortment of bakery products which are produced in excess to fulfill the consumers demands. There are limited possibilities for reprocessing bread waste in the bakeries. Some wastes can be processed into bread crumbs, as a replacement of part of flour in sourdough preparation or as animal feed. However due to often microbial spoilage its use for human and animal nutrition could be risky for health of the consumers. These problems are the reason why waste bread is most often left on landfills or used as a fuel for combustion. The most promising solution for waste bread utilization is use it as a raw material for ethanol fuel production. Earlier studies shown that waste bread is a high-yielding material for ethanol fermentation. The amount of ethanol produced from bread waste that shown no signs of mould contamination, depending on processing technology, ranged as mentioned by the authorsca. 350–370 g kgÀ1 of feedstock dry matter. Kawa-Rygielska and Pietrzak studied the possibility of using waste bread showing high level of surface mould contamination for ethanol production, this resulted in a decrease of ethanol yield in comparison to non contaminated material (ca. 230–250 g kgÀ1 depending on the raw material loading in the fermentation feed). The other possibilities for waste bread utilization via biotechnological processes are in example: solid state fermentation by Aspergillus awamori for production of amylases and proteases, biohydrogen production using rhizosphere microflora, succinic acid production by Actinobacillus succinogenes or aromatic compounds production by Geotrichum candidum.
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1. Introduction
Ethanol is considered as one of the most promising renewable fuel that can replace fossil fuels-based transportation fuels. It is most commonly produced by microbial (most often yeast) catalyzed fermentation using plant biomass as a raw material. Starchy raw materials (i.e. corn, wheat, sorghum) are still the most common feed-stocks for fuel ethanol production in temperate climate regions of the world (Europe, North America, Central Asia). However its use as fuel production resources may affect on the prices of food products manufactured from them. The use of non-edible parts of the plant (straws, stalks), known as the lignocellulose biomass, as the raw material in distillery is nowadays considered as the most promising opportunity for ethanol production that does not affect the prices of foodstuffs. However, the conversion of lignocellusosic biomass into ferment-able sugars and, subsequently into ethanol requires high temperature pretreatment which is often catalyzed using corrosive, non-ecological or costly agents like acids, alkali, ionic liquids and others. Moreover the efficiency of saccharification and fermentation of lignocellulose is still much less efficient in comparison to starches, but starchy raw materials are very costly and the cost of the feedstock can exceed 65% of the price of final product. The solution to the problems of affecting food prices by using agricultural crops for fuel production and the technological difficulties with conversion of lignocellulosic biomass is utilization of food industry wastes for production of biofuels. One of the most promising food waste that can be processed into ethanol is waste bread. It contains significant amount of starch that is easily hydrolyzed to monomeric sugars using amylases, the amount of starch and simple sugars in bread ranges 500–750 and 3–50 g kgÀ1 respectively. Moreover bread contains 100–150 g kgÀ1
of protein which, after hydrolysis to peptides and amino acids, is essential for yeast growth and accelerated fermentation. Waste bread is also highly accessible raw material for ethanol processing. The estimated wastage for bakery products ranges 7–10% of its total production, taking into consideration estimated world annual production of bread which is about 100 million tones the amount of generated waste can reach even 10 million tones per year worldwide. The major factor for bread waste formation is that part of the produced product is left unsold and is returned to the bakery due to significant level of staling and large amount of available assortment of bakery products which are produced in excess to fulfill the consumers demands. There are limited possibilities for reprocessing bread waste in the bakeries. Some wastes can be processed into bread crumbs, as a replacement of part of flour in sourdough preparation or as animal feed. However due to often microbial spoilage its use for human and animal nutrition could be risky for health of the consumers. These problems are the reason why waste bread is most often left on landfills or used as a fuel for combustion. The most promising solution for waste bread utilization is use it as a raw material for ethanol fuel production. Earlier studies shown that waste bread is a high-yielding material for ethanol fermentation. The amount of ethanol produced from bread waste that shown no signs of mould contamination, depending on processing technology, ranged as mentioned by the authorsca. 350–370 g kgÀ1 of feedstock dry matter. Kawa-Rygielska and Pietrzak studied the possibility of using waste bread showing high level of surface mould contamination for ethanol production, this resulted in a decrease of ethanol yield in comparison to non contaminated material (ca. 230–250 g kgÀ1 depending on the raw material loading in the fermentation feed). The other possibilities for waste bread utilization via biotechnological processes are in example: solid state fermentation by Aspergillus awamori for production of amylases and proteases, biohydrogen production using rhizosphere microflora, succinic acid production by Actinobacillus succinogenes or aromatic compounds production by Geotrichum candidum.
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