Ozlem Akpinar

Production of xylooligosaccharides by controlled acid hydrolysis of lignocellulosic materials.

Different agricultural wastes, namely tobacco stalk (TS), cotton stalk (CS), sunflower stalk (SS), and wheat straw (WS), were used for the production of xylooligosaccharide (XO). XO production was performed by acid hydrolysis of xylan, which was obtained by alkali extraction from these agricultural wastes. The major component of these agricultural wastes was determined as cellulose (30-42%), followed by xylan (20%) and lignin (20-27%). Xylans from these wastes had mainly xylose (85-96%) with small amount of glucose, while wheat straw xylan contained also arabinose. The best xylan conversion into XOs was achieved with 0.25M H(2)SO(4) with 30-min reaction time. Under these conditions, the XO yield was between 8% and 13%. The yield of XOs depends on both acid concentration and hydrolysis time, but the yield of monosaccharide depends on the structure and composition of xylan besides acid concentration and the time. The more branched xylan, WSX, gave the highest monosaccharide ( approximately 16%) and furfural ( approximately 49mg/100g xylan) yield. This research showed that all xylans from selected agricultural wastes generated XOs with similar profiles, and these oligosaccharides could be used as functional food ingredients or soluble substrates for xylanases.

Preparation of Methyl 6‐O‐p‐Nitrobenzoyl‐β‐d‐Glucoside

Methyl 6‐O‐p‐nitrobenzoyl‐β‐d‐glucoside was synthesized by reacting methyl 4,6‐O‐p‐nitrobenzylidine‐β‐d‐glucoside with N‐bromosuccinimide (NBS). First, methyl β‐d‐glucoside was converted into methyl 4,6‐O‐p‐nitrobenzylidine‐β‐d‐glucoside with p‐nitrobenzaldehyde. Later, methyl 4,6‐O‐p‐nitrobenzylidine‐β‐d‐glucoside was opened oxidatively with NBS to give methyl 6‐O‐p‐nitrobenzoyl‐β‐d‐glucoside.

Evaluation of cotton stalk hydrolysate for xylitol production

ABSTRACT Cotton stalk is a widely distributed and abundant lignocellulosic waste found in Turkey. Because of its rich xylose content, it can be a promising source for the production of xylitol. Xylitol can be produced by chemical or biotechnological methods. Because the biotechnological method is a simple process with great substrate specificity and low energy requirements, it is more of an economic alternative for the xylitol production. This study aimed to use cotton stalk for the production of xylitol with Candida tropicalis Kuen 1022. For this purpose, the combined effects of different oxygen concentration, inoculum level and substrate concentration were investigated to obtain high xylitol yield and volumetric xylitol production rate. Candida tropicalis Kuen 1022 afforded different concentrations of xylitol depending on xylose concentration, inoculum level, and oxygen concentration. The optimum xylose, yeast concentration, and airflow rate for cotton stalk hydrolysate were found as 10.41 g L−1, 0.99 g L−1, and 1.02 vvm, respectively, and under these conditions, xylitol yield and volumetric xylitol production rate were obtained as 36% and 0.06 g L−1 hr−1, respectively. The results of this study show that cotton stalk can serve as a potential renewable source for the production of xylitol.

Gıda Amaçlı Sellooligosakkaritlerin Hazırlanması ve Saflaştırılması 1

The chromatographic separation of cellooligosaccharides using cellulose as a stationary phase was studied. The driving force of the work is the current interest in using cellooligosaccharides as functional non- digestible oligosaccharides in foods. The studies presented here illustrate the potential of using ethanol-water mobile phases in conjunction with cellulose stationary phases for cellooligosaccharide fractionation. The interaction between cellulose and cellooligosaccharide in ethanol-water mixtures and their elution order from cellulose-based columns using ethanol-water mobile phases were shown to be in line with their degree of polymerization (DP); the higher DP cellooligosaccharides being less soluble and having longer retention times. Microcrystalline cellulose was shown to work as chromatographic stationary phases. The results demonstrated that cellotetraose and cellopenlaose could be obtained in relatively pure form using a cellulose stationary phase with a 20% ethanol mobile phase at room temperature.