Effect of overliming and activated carbon detoxification on inhibitors removal and butanol fermentation of poplar prehydrolysates

Abstract

BackgroundBiomass prehydrolysates from dilute acid pretreatment contain a considerable amount of fermentable sugars for biofuels production. However, carbonyl degradation compounds present severe toxicity to fermentation microbes. Furans (such as furfural and hydroxymethylfurfural), aliphatic acids (such as acetic acid, formic acid and levulinic acid) and phenolic compounds (such as vanillin and syringaldehyde) have been suggested to be the main inhibitors in biomass prehydrolysates. However, no single compound has been determined as the dominant toxic inhibitor. The effects of various detoxification methods on inhibitors removal have not been fully understood.ResultsThe effects of overliming and activated carbon (AC) detoxification on the removal of inhibitors and butanol fermentation of the poplar prehydrolysates were investigated. Gas chromatography–mass spectrometry (GC/MS) was used to identify and quantify 46 carbonyl compounds as potential inhibitors. It was observed that overliming and AC treatment alone did not make the prehydrolysates fermentable with Clostridium saccharobutylicum. The sequential overliming and AC resulted in a remarkable fermentability and a high butanol yield at 0.22 g g−1 sugar. The inhibitor removal in the prehydrolysates treated by overliming and AC was also examined by GC/MS. Overliming removed 75.6% of furan derivatives and 68.1% of aromatic monomers. In comparison, AC (5.0% w/v) removed 77.9% of furan derivatives and 98.6% of aromatic monomers. In addition, overliming removed much more 2,5-furandicarboxyaldehyde, 5-ethylfuran-2-carbaldehyde and 2,5-hexanedione than AC did. On the contrary, AC could remove considerably more phenolic acids than overliming. In the sequential detoxification, both dialdehydes/diketones and phenolic acids were extensively removed. This could be the main reason why the sequential detoxification enabled a remarkable ABE fermentation for the prehydrolysates.ConclusionsThis study indicated that the effect of overliming and AC treatment on inhibitors removal was related to their chemical structures. Overliming removed more dialdehydes and diketones than AC treatment, while AC removed more phenolic acids than overliming. Sequential overliming and AC treatment were required to make the prehydrolysates fermentable with C. saccharobutylicum. The study also suggested different detoxification method was needed for ABE fermentation of the prehydrolysate as compared to ethanol fermentation.Electronic supplementary materialThe online version of this article (10.1186/s13068-018-1182-0) contains supplementary material, which is available to authorized users.

Oxygen radical based on non-thermal atmospheric pressure plasma alleviates lignin-derived phenolic toxicity in yeast

“…Because vanillin is a potent inhibitor of yeast-specific ethanol fermentation via dose-dependent blockage of yeast growth and subsequent fermentation, vanillin toxicity represents a major barrier to reducing the cost of bioethanol production [17][18][19][20]. Several methods, including overliming, anion-exchange resin treatment, activated carbon treatment, sulphate treatment, and treatment with laccase, have been proposed to alleviate the negative effects of lignin-derived phenolics on biomass hydrolysates [21][22][23][24][25]; however, these methods require long processing times and are detrimental to the environment based on the release of organic waste [21,23]. Additionally, utilization of these methods requires alkaline-or acid-resistant equipment, a neutralization step, chemical recovery, and waste treatment [21][22][23][24][25].…”

“…Several methods, including overliming, anion-exchange resin treatment, activated carbon treatment, sulphate treatment, and treatment with laccase, have been proposed to alleviate the negative effects of lignin-derived phenolics on biomass hydrolysates [21][22][23][24][25]; however, these methods require long processing times and are detrimental to the environment based on the release of organic waste [21,23]. Additionally, utilization of these methods requires alkaline-or acid-resistant equipment, a neutralization step, chemical recovery, and waste treatment [21][22][23][24][25]. Therefore, the development of an environmentally friendly vanillin-removal process is an important prerequisite for the efficient production of bioethanol from lignocellulosic biomass.…”

Tequila Agave Bagasse Hydrolysate for the Production of Polyhydroxybutyrate by Burkholderia sacchari

“…Other compounds present in the hydrolysate (such as salts) might inhibit to a certain extent the enzyme activity. This is a probable reason why the elimination of phenolic compounds did The detoxification with activated charcoal is a treatment frequently used to purify or to recover certain compounds from hydrolysates (lignin, tannin, furan derivatives, aromatic monomers, and phenolic acids) [29,30]. The pH of the hydrolysate, the concentration of activated carbon used, and the contact time are known factors that can influence the effectivity of the detoxification process with this adsorbent [31,32].…”

Effect of detoxification methods on ABE production from corn stover hydrolysate by Clostridium acetobutylicum CICC 8016

“…There are different detoxification methods including treatments through overliming by addition of Ca(OH) 2 or CaO, adsorptions by activated charcoals and resins, evaporation, steam stripping, as well as the combined methods, which have been well summarized in recent review publications . The overliming treatment process, which increases hydrolysate pH to ∼10–12 by lime, followed by reducing pH to cultivation pH by H 2 SO 4 , is very effective in removal of furans such as furfural and HMF but has limited effects on aliphatic acids such as acetic acid, formic acid, and levulinic acid . Activated carbon/charcoal treatment has similar effects on removal of furans and phenolic compounds though the extents of removal are different .…”