TY - JOUR
T1 - Process optimization for recycling of bread waste into bioethanol and biomethane
T2 - A circular economy approach
AU - Narisetty, Vivek
AU - Nagarajan, Sanjay
AU - Gadkari, Siddharth
AU - Ranade, Vivek V.
AU - Zhang, Jingxin
AU - Patchigolla, Kumar
AU - Bhatnagar, Amit
AU - Kumar Awasthi, Mukesh
AU - Pandey, Ashok
AU - Kumar, Vinod
N1 - Funding Information:
The authors would like to thank Prof Sunghoon Park from Ulsan National Institute of Science and Technology, South Korea for providing Saccharomyces cerevisiae KL17 strain. We would also like to express our gratitude to Novozymes for kindly providing the Dextrozyme peak enzymes for this work. We acknowledge Cranfield University for providing analytical facilities for conducting the experiments. Conceptualization, Investigation, Methodology was carried out by VN, SN, and SG. VN, SN, SG and VK were involved in data curation, formal analysis, and writing original draft. VVR, JZ, and KP were involved in conceptualization, and methodology. AB, MKA, and AP were involved in writing – review & editing the manuscript. All authors read and approved the final manuscript. All data generated or analyzed during this study are included in the Manuscript.
Publisher Copyright:
© 2022 The Authors
PY - 2022/8/15
Y1 - 2022/8/15
N2 - Bread is the second most wasted food in the UK with annual wastage of 292,000 tons. In the present work, bread waste (BW) was utilized for fermentative production of ethanol by Saccharomyces cerevisiae KL17. Acidic and enzymatic saccharification of BW was carried out resulting in the highest glucose release of 75 and 97.9 g/L which is 73.5 and 95.9% of theoretical yield, respectively. The obtained sugars were fermented into ethanol initially in shake flask followed by scale up in bioreactor in batch and fed-batch mode. In the fed-batch mode of cultivation, the maximum ethanol titers of 111.3, 106.9, and 114.9 g/L with conversion yield and productivity of 0.48, 0.47, and 0.49 g/g, and 3.1, 3.0, and 3.2 g/L.h was achieved from pure glucose, glucose-rich acidic and enzymatic hydrolysates, respectively. Further to improve the process economics, the solid residues after acidic (ABW) and enzymatic (EBW) hydrolysis of BW along with respective fermentation residues (FR) obtained after the ethanol production were pooled and subjected to anaerobic digestion. The solid residue from ABW + FR, and EBW + FR yielded a biochemical methanation potential (BMP) of 345 and 379 mL CH4/g VS, respectively. Life cycle assessment of the process showed that the total emissions for ethanol production from BW were comparable to the emissions from more established feedstocks such as sugarcane and maize grain and much lower when compared to wheat and sweet potato. The current work demonstrates BW as promising feedstock for sustainable biofuel production with the aid of circular biorefining strategy. To the authors knowledge, this is the first time, such a sequential system has been investigated with BW for ethanol and biomethane production. Further work will be aimed at ethanol production at pilot scale and BMP will be accessed in a commercial anaerobic digester.
AB - Bread is the second most wasted food in the UK with annual wastage of 292,000 tons. In the present work, bread waste (BW) was utilized for fermentative production of ethanol by Saccharomyces cerevisiae KL17. Acidic and enzymatic saccharification of BW was carried out resulting in the highest glucose release of 75 and 97.9 g/L which is 73.5 and 95.9% of theoretical yield, respectively. The obtained sugars were fermented into ethanol initially in shake flask followed by scale up in bioreactor in batch and fed-batch mode. In the fed-batch mode of cultivation, the maximum ethanol titers of 111.3, 106.9, and 114.9 g/L with conversion yield and productivity of 0.48, 0.47, and 0.49 g/g, and 3.1, 3.0, and 3.2 g/L.h was achieved from pure glucose, glucose-rich acidic and enzymatic hydrolysates, respectively. Further to improve the process economics, the solid residues after acidic (ABW) and enzymatic (EBW) hydrolysis of BW along with respective fermentation residues (FR) obtained after the ethanol production were pooled and subjected to anaerobic digestion. The solid residue from ABW + FR, and EBW + FR yielded a biochemical methanation potential (BMP) of 345 and 379 mL CH4/g VS, respectively. Life cycle assessment of the process showed that the total emissions for ethanol production from BW were comparable to the emissions from more established feedstocks such as sugarcane and maize grain and much lower when compared to wheat and sweet potato. The current work demonstrates BW as promising feedstock for sustainable biofuel production with the aid of circular biorefining strategy. To the authors knowledge, this is the first time, such a sequential system has been investigated with BW for ethanol and biomethane production. Further work will be aimed at ethanol production at pilot scale and BMP will be accessed in a commercial anaerobic digester.
KW - Bioethanol
KW - Biomethane
KW - Bread waste
KW - Life cycle assessment
KW - Saccharification
KW - Saccharomyces cerevisiae
U2 - 10.1016/j.enconman.2022.115784
DO - 10.1016/j.enconman.2022.115784
M3 - Article
AN - SCOPUS:85131136211
SN - 0196-8904
VL - 266
JO - Energy Conversion and Management
JF - Energy Conversion and Management
M1 - 115784
ER -
