Effect of inoculum to substrate ratio on the hydrolysis and acidification of food waste in leach bed reactor

Su Yun Xu, Obuli P. Karthikeyan, Ammaiyappan Selvam, Jonathan W C Wong*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

90 Citations (Scopus)


The aim of present study was to determine an appropriate ISR (inoculum to substrate ratio) to enhance the hydrolysis rate and reduce the solid retention time of food waste in hydrolytic-acidogenesis leach bed reactor (LBR). LBR 1–4 were inoculated with 0%, 5%, 20% and 80% (w/w basis) of anaerobically digested sludge, respectively, using artificial food waste as substrate. Experiments were conducted in batch mode at mesophilic condition (35 °C) for 17 days. Higher ISR resulted in 4.3-fold increase in protein hydrolysis; whereas, only a modest increase in the decomposition of carbohydrate. Two kinetic models for carbohydrate and protein degradation were proposed and evaluated. The differences among four ISRs in volatile solids removal efficiencies were marginal, i.e. 52.4%, 62.8%, 63.2% and 71.7% for LBR 1–4, respectively; indicating that higher ISR was insignificant in enhancing the overall hydrolysis rate in LBR. Therefore, a lower ISR of 20% was recommended in the hydrolytic-acidogenic process.

Original languageEnglish
Pages (from-to)425-430
Number of pages6
JournalBioresource Technology
Publication statusPublished - Dec 2012

Scopus Subject Areas

  • Bioengineering
  • Environmental Engineering
  • Renewable Energy, Sustainability and the Environment
  • Waste Management and Disposal

User-Defined Keywords

  • Acidogenesis
  • Anaerobic digestion
  • Inoculum to substrate ratio
  • Kinetics study
  • Proteolytic bacteria


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