Bioaugmentation enhances dark fermentative hydrogen production in cultures exposed to short-term temperature fluctuations

Onyinye Okonkwo,Rahul Mangayil,Renaud Escudie,Nicolas Bernet,Aino-Maija Lakaniemi,Eric Trably

doi:10.1007/s00253-019-10203-8

Abstract

Hydrogen-producing mixed cultures were subjected to a 48-h downward or upward temperature fluctuation from 55 to 35 or 75 °C. Hydrogen production was monitored during the fluctuations and for three consecutive batch cultivations at 55 °C to evaluate the impact of temperature fluctuations and bioaugmentation with synthetic mixed culture of known H2 producers either during or after the fluctuation. Without augmentation, H2 production was significantly reduced during the downward temperature fluctuation and no H2 was produced during the upward fluctuation. H2 production improved significantly during temperature fluctuation when bioaugmentation was applied to cultures exposed to downward or upward temperatures. However, when bioaugmentation was applied after the fluctuation, i.e., when the cultures were returned to 55 °C, the H2 yields obtained were between 1.6 and 5% higher than when bioaugmentation was applied during the fluctuation. Thus, the results indicate the usefulness of bioaugmentation in process recovery, especially if bioaugmentation time is optimised.

Highlights

Biological methods for H2 production, including biophotolysis, photo fermentation, dark fermentation and biocatalysed electrolysis, have received increasing attention due to their ability to utilise renewable feedstocks such as organic wastes, plant biomass residues or sunlight for H2 generation (Hallenbeck and Benemann 2002; Dincer 2012)
We showed that effects of temporal temperature fluctuations on dark fermentative H2 production were more severe during and after upward temperature fluctuations than during and after downward temperature fluctuations (Okonkwo et al 2019)
Bacteria belonging to the genera Thermoanaerobacter, Caldicellulosiruptor, Clostridium, Thermoanaerobacterium and Thermotoga were added to the synthetic mixed culture that was used for bioaugmentation in this study

Summary

Introduction

Biological methods for H2 production, including biophotolysis, photo fermentation, dark fermentation and biocatalysed electrolysis, have received increasing attention due to their ability to utilise renewable feedstocks such as organic wastes, plant biomass residues or sunlight for H2 generation (Hallenbeck and Benemann 2002; Dincer 2012). Dark fermentative H2 production can be carried out at mesophilic, thermophilic and hyperthermophilic conditions (Shin et al 2004; Kargi et al 2012) but is thermodynamically more favourable at higher temperatures Thermophilic processes are typically more sensitive to temperature fluctuations and require more consistent organic loading rate than mesophilic dark fermentation processes (Angelidaki and Ahring 1994). A sudden, even transient temperature changes can produce varying responses in microbial populations resulting in an imbalanced metabolism and low process performance (Jiang and Morin 2007; Okonkwo et al 2019)

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