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Effects of Ca(OH) 2 treatments (“overliming”) on the composition and toxicity of bagasse hemicellulose hydrolysates
Author(s) -
Martinez Alfredo,
Rodriguez Maria E.,
York Sean W.,
Preston James F.,
Ingram Lonnie O.
Publication year - 2000
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/1097-0290(20000905)69:5<526::aid-bit7>3.0.co;2-e
Subject(s) - hemicellulose , hydrolysate , furfural , chemistry , levulinic acid , hydroxymethylfurfural , bagasse , xylose , fermentation , acetic acid , chromatography , bioconversion , food science , hydrolysis , biochemistry , microbiology and biotechnology , biology , catalysis
Hemicellulose syrups from dilute sulfuric acid hydrolysates of hemicellulose contain inhibitors that prevent efficient fermentation by yeast or bacteria. It is well known that the toxicity of these hydrolysate syrups can be ameliorated by optimized “overliming” with Ca(OH) 2 . We have investigated the optimization of overliming treatments for sugar cane bagasse hydrolysates (primarily pentose sugars) using recombinant Escherichia coli LY01 as the biocatalyst. A comparison of composition before and after optimal overliming revealed a substantial reduction in furfural, hydroxymethylfurfural, and three unidentified high‐performance liquid chromatography (HPLC) peaks. Organic acids (acetic, formic, levulinic) were not affected. Similar changes have been reported after overliming of spruce hemicellulose hydrolysates (Larsson et al., 1999). Our studies further demonstrated that the extent of furan reduction correlated with increasing fermentability. However, furan reduction was not the sole cause for reduced toxicity. After optimal overliming, bagasse hydrolysate was rapidly and efficiently fermented (>90% yield) by LY01. During these studies, titration, and conductivity were found to be in excellent agreement as methods to estimate sulfuric acid content. Titration was also found to provide an estimate of total organic acids in hydrolysate, which agreed well with the sum of acetic, levulinic, and formic acids obtained by HPLC. Titration of acids, measurement of pH before and after treatment, and furan analyses are proposed as relatively simple methods to monitor the reproducibility of hydrolysate preparations and the effectiveness of overliming treatments. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 69: 526–536, 2000.