High-Level fermentative production of Lactic acid from bread waste under Non-sterile conditions with a circular biorefining approach and zero waste discharge

Rylan Cox, Vivek Narisetty, Sanjay Nagarajan, Deepti Agrawal, Vivek V. Ranade, Konstantinos Salonitis, Joachim Venus, Vinod Kumar

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23 Citations (SciVal)
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Abstract

Bread waste (BW) is a severe solid waste management problem in Europe. The current study demonstrates an environment-friendly solution by valorising BW into lactic acid (LA) and the corresponding solid residues generated during hydrolysis and fermentation to biogas. To this end, BW was saccharified through acidic and enzymatic hydrolysis, and the hydrolysate obtained was used for LA fermentation under non-sterile conditions using thermophilic Bacillus coagulans DSM1. Maximum glucose concentration achieved during acid hydrolysis with 2% (v/v) acid loading and 20% (w/v) solid loading was 67.9 g/L glucose, with a yield of 0.34 g/g BW. The LA accumulated with concentrated BW acid hydrolysate was 102.4 g/L with yield and productivity of 0.75 g/g and 1.42 g/L. h, respectively. For enzymatic hydrolysis, three commercial amylase preparations (Amyloglucosidase, Spirizyme, Dextrozyme) were employed. The highest glucose release (98.6 g/L) and yield (0.49 g glucose/g BW) was attained with Dextrozyme from Novozymes. The fed-batch fermentation by B. coagulans was conducted, using commercial glucose and glucose-rich BW hydrolysate from Dextrozyme. The LA titer, yield and productivity obtained with pure glucose were 222.7 g/L, 0.92 g/g and 1.86 g/L.h, respectively, whereas BW hydrolysate (BWH) resulted in 155.4 g/L LA, with a conversion yield and productivity of 0.85 g/g glucose and 1.30 g/L. h, respectively. Further to the LA biosynthesis, the solid residues generated during hydrolysis and fermentation were subjected to biogas generation, resulting in 553 mL CH4/g volatile solids under batch mode. This massive LA titer amassed under non-sterile conditions and integrated biogas production using fermented residues demonstrates a high potential for an integrated biorefinery based on BW.
Original languageEnglish
Article number122976
JournalFuel
Volume313
Early online date5 Jan 2022
DOIs
Publication statusPublished - 1 Apr 2022

Bibliographical note

Funding Information:
The author Rylan Cox would like to thank Engineering and Physical Research Council (EPSRC) (Budget code EP/L016389/1 ) for funding his doctoral research. The funders had no role in study design, data collection and analysis, decision to publish, nor preparation of the article. We acknowledge Cranfield University for providing analytical facilities for conducting the experiments.

Funding Information:
The author Rylan Cox would like to thank Engineering and Physical Research Council (EPSRC) (Budget code EP/L016389/1) for funding his doctoral research. The funders had no role in study design, data collection and analysis, decision to publish, nor preparation of the article. We acknowledge Cranfield University for providing analytical facilities for conducting the experiments. RC, VN and SN carried out all the experimental work. RC, VN, SN, VVR and VK analyzed the data and wrote the manuscript. DA, KS and JV were involved in proofreading the Manuscript and revised it critically. All authors read and approved the final manuscript.

Publisher Copyright:
© 2021

Keywords

  • Acidic/Enzymatic hydrolysis
  • Bacillus coagulans
  • Biochemical methanation potential
  • Bread waste
  • Lactic acid
  • Non-sterile conditions

ASJC Scopus subject areas

  • General Chemical Engineering
  • Fuel Technology
  • Energy Engineering and Power Technology
  • Organic Chemistry

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