Xylitol production from xylose mother liquor: a novel strategy that combines the use of recombinant Bacillus subtilis and Candida maltosa

Abstract

BackgroundXylose mother liquor has high concentrations of xylose (35%-40%) as well as other sugars such as L-arabinose (10%-15%), galactose (8%-10%), glucose (8%-10%), and other minor sugars. Due to the complexity of this mother liquor, further isolation of xylose by simple method is not possible. In China, more than 50,000 metric tons of xylose mother liquor was produced in 2009, and the management of sugars like xylose that present in the low-cost liquor is a problem.ResultsWe designed a novel strategy in which Bacillus subtilis and Candida maltosa were combined and used to convert xylose in this mother liquor to xylitol, a product of higher value. First, the xylose mother liquor was detoxified with the yeast C. maltosa to remove furfural and 5-hydromethylfurfural (HMF), which are inhibitors of B. subtilis growth. The glucose present in the mother liquor was also depleted by this yeast, which was an added advantage because glucose causes carbon catabolite repression in B. subtilis. This detoxification treatment resulted in an inhibitor-free mother liquor, and the C. maltosa cells could be reused as biocatalysts at a later stage to reduce xylose to xylitol. In the second step, a recombinant B. subtilis strain with a disrupted xylose isomerase gene was constructed. The detoxified xylose mother liquor was used as the medium for recombinant B. subtilis cultivation, and this led to L-arabinose depletion and xylose enrichment of the medium. In the third step, the xylose was further reduced to xylitol by C. maltosa cells, and crystallized xylitol was obtained from this yeast transformation medium. C. maltosa transformation of the xylose-enriched medium resulted in xylitol with 4.25 g L-1·h-1 volumetric productivity and 0.85 g xylitol/g xylose specific productivity.ConclusionIn this study, we developed a biological method for the purification of xylose from xylose mother liquor and subsequent preparation of xylitol by C. maltosa-mediated biohydrogenation of xylose.

Production of validamycin A from hemicellulose hydrolysate by Streptomyces hygroscopicus 5008

“…Corncob hydrolysate containing approximately 500 g L À1 D-xylose, 190 g L À1 L-arabinose and 150 g L À1 D-glucose was supplied by Jiahe Sugar Co., Ltd., Shandong, China (Cheng et al, 2011). The seed medium containing 2% (v/v) corncob hydrolysate, 2.2 g L À1 soybean meal, 10 g L À1 yeast extract, 2 g L À1 NaCl and 0.8 g L À1 KH 2 PO 4 was used for corncob hydrolysate fermentation.…”

“…It is an acid hydrolysate waste which is generated during the industrial-scale production of D-xylose from corncob (Wang et al, 2010). Corncob hydrolysate contains a high concentration of mixed sugars (including D-xylose, L-arabinose and D-glucose) and D-xylose occupies their two-third amount (Cheng et al, 2011). Recently, this low cost and high carbohydrate content feedstock has attracted increasing attention for the production of industrially important chemicals such as acetone, butanol and ethanol (Xiao et al, 2012), propionic acid , L-lactic acid (Wang et al, 2010), and xylitol (Cheng et al, 2011).…”

“…Corncob hydrolysate contains a high concentration of mixed sugars (including D-xylose, L-arabinose and D-glucose) and D-xylose occupies their two-third amount (Cheng et al, 2011). Recently, this low cost and high carbohydrate content feedstock has attracted increasing attention for the production of industrially important chemicals such as acetone, butanol and ethanol (Xiao et al, 2012), propionic acid , L-lactic acid (Wang et al, 2010), and xylitol (Cheng et al, 2011). However, there is still lack of reports on application of such cheap feedstocks to produce commercially interesting antibiotics like VAL-A.…”

Effects of pH and Aeration Conditions on Xylitol Production by Candida and Hansenula Yeasts

“…However, xylose and arabinose are not metabolized by the most microorganisms, until glucose is present in the medium [11]. This regulation called carbon catabolite repression prevents the uptake and catabolism of less favourable carbon sources [11,15,20,21]. The pH value is also important for the optimal production of xylitol.…”

“…The concentration of different monosaccharides and vitamins also play a major role in the production of xylitol [1,11,20]. An ideal strategy employed in xylitol biotechnological production is that glucose and arabinose can be used to supply energy for the cell growth, while xylose can be used for xylitol production.…”