Valorization of crude glycerol and eggshell biowaste as media components for hydrogen production: A scale-up study using co-culture system

Abstract

The properties of eggshells (EGS) as neutralizing and immobilizing agent were investigated for hydrogen (H) production using crude glycerol (CG) by co-culture system. Eggshells of different sizes and concentrations were used during batch and repeated-batch fermentation. For batch and repeated-batch fermentation, the maximum H production (36.53±0.53 and 41.16±0.95mmol/L, respectively) was obtained with the EGS size of 33μm<x<75μm. Hydrogen production increased with the decreasing size of EGS. Eggshells maintained the fermentation pH (6.00-6.30) and provided immobilization support as confirmed by scanning electron microscopy. As media components, the EGS concentration of 0.25% (w/v) was found to be optimum for maximum H production (31.66±0.55mmol/L) and the production profile was comparable to H production (32.07±0.92mmol/L) obtained with all media components. In scale-up study with semi-continuous bioreactor (7.5L), almost 1.5-fold increase (in comparison to mono-culture) i.e. 312.12mmol-H/L-of medium with 86.65% glycerol utilization was obtained.

Bioconversion of crude glycerol from waste cooking oils into hydrogen by sub-tropical mixed and pure cultures

“…Biodiesel industry generates large amounts of crude glycerol as co-product, being 10 kg for each 100 kg of biodiesel produced [11]. With global production of biodiesel crossing 20 billion liters, very large quantities of glycerol will be generated [10].…”

Advances and Applications of Clostridium Co-culture Systems in Biotechnology

“…The sixth advantage is the scalability of Clostridium co-culture systems. In addition to laboratory-scale anaerobic bottle or shake bottle studies, larger fermentation tanks or bioreactors have been used in the Clostridium co-culture system and have been proved to have significant effects, like eliminating substrate inhibition (Pachapur et al, 2016a), increasing product yield (Zhang et al, 2012;Salimi and Mahadevan, 2013;Luo et al, 2017;Morsy, 2017;Kim et al, 2018;Cheng et al, 2019), showing good stability (Masset et al, 2012) and continuous and stable product generation (Barca et al, 2016;Wu et al, 2016).…”

“…In addition, RT-PCR was used to analyze the expression levels of key pathway genes to better understand the interactions in the Clostridium co-culture system (Benomar et al, 2015;Wang et al, 2016;Lu et al, 2017). Furthermore, flow cytometry, fluorescence microscopy, scanning electron microscopy (SEM), and a specific genetic marker were also utilized to elucidate bacterial strain interactions in the Clostridium co-culture system (Benomar et al, 2015;Pachapur et al, 2016a). Charubin and Papoutsakis established a transwell system utilizing a permeable membrane allowing metabolite exchange between both compartments and used quantitative PCR (qPCR) for population analysis and RT-qPCR for gene expression analysis.…”

“…Eventually pH 7 was determined to be the best condition for bacterial cooperation during a combined process to produce hydrogen through optimization of a co-culture of solventogenic Clostridia and anoxygenic phototrophic bacteria (Zagrodnik and Laniecki, 2015). In addition, adjustment of the phosphate buffer concentration , adopting a fixed pH value (Zagrodnik and Laniecki, 2015), and addition of exogenous regulators such as eggshell biowaste (Pachapur et al, 2016a) were also shown to be good pH control strategies in many Clostridium co-culture systems. Moreover, co-culture of immobilized cells will be less affected by changes in medium pH and thus promote system stability and yield, which is also considered a good strategy (Xu and Tschirner, 2014).…”

Seed Pretreatment for Increased Hydrogen Production Using Mixed-Culture Systems with Advantages over Pure-Culture Systems

“…The Scanning Electron Microscope (SEM) image analysis illustrates the physical appearance of hydrogen-producing bacteria from the rod-shaped morphology in case of heat-pretreated and non-treated soil inocula [46]. SEM analysis examines the cellular level and can be performed for the qualitative assessment of the hydrogen-producing microorganisms [129]. In addition to the determination of molecular profiling, SEM can also be used to identify the cellular destruction of corn stover after hydrolysis.…”