Growth ofAureobasidium pullulans on waste water hemicelluloses

Strain Aureobasidium pullulans capable of utilizing hemicelluloses and xylan was cultivated on processed waste dialysis liquor from the production of viscose fibres, containing about 1.5% hemocelluloses. Basic conditions of biomass production were tested on a laboratory scale. The dialysis waste liquor adjusted with mineral acids to pH 4--5 and supplemented with 0.05% yeast autolyzate and 0.2% ammonium sulphate affords protein yields of about 0.8 g/l, corresponding to 4.0--4.5 g dry biomass. Biomass is isolated together with residual water-insoluble hemicelluloses which are not utilized by the microorganism. The total utilization of hemicelluloses attains about 70%.     

Fractional purification and bioconversion of hemicelluloses

Hemicelluloses are types of plant cell wall polysaccharides, and the world's second most abundant renewable polymers after cellulose in lignocellulosic materials. They represent a type of hetero-polysaccharide with complex structure containing glucose, xylose, mannose, galactose, arabinose, rhamnose, glucuronic acid, and galacturonic acid in various amounts, depending on the source. Hemicelluloses are usually bonded to other cell-wall components such as cellulose, cell-wall proteins, lignin, and phenolic compounds by covalent and hydrogen bonds, and by ionic and hydrophobic interactions. This paper provides a review on hemicelluloses from lignocellulosic materials, especially in regard to their isolation and purification methods, and bioconversion. Current isolation and purification strategies are summarized, including: alkali peroxide extraction, organic solvent extraction, steam explosion, ultrasound-assisted extraction, microwave-assisted extraction, column chromatography, and membrane separation. In addition, the bioconversion of hemicelluloses including pretreatment, enzymatic hydrolysis, and fermentation are discussed.     

Bioconversion of hemicelluloses into fungal protein

Summary The utilization of cellulose from one ton of lignocellulose for ethanol production would yield 150–250 kg of hemicelluloses. The total soluble solids in the hemicellulose fraction (HF) obtained with the Université de Sherbrooke (UdeS) process contained about 56% carbohydrates. These carbohydrates were present in the form of oligomers of various sugars, predominantly xylose. All the test fungi,Chaetomium cellulolyticum, C. cellulolyticum (asporogenous mutant) andPleurotus sajor-caju, were capable of utilizing all the carbohydrates present in HF.C. cellulolyticum gave the highest amount of protein (7 g/l) from 19 g carbohydrates/l. The yield of protein was higher than expected, indicating that carbon compounds other than reducing sugars present in HF might have been consumed for fungal growth. The inhibitory effect of toxic compounds on protein production increased with an increase in concentration of soluble solids in HF. The inhibitory effect was overcome by increasing the pH of the medium to 6.0 or 7.0. Fungal protein production from hemicelluloses will give extra revenue in our integrated approach for ethanol production from lignocelluloses.NRCC publication No. 26277.     

Cellulose and hemicelluloses recovery from grape stalks

In this work, two mild chemical fractionation procedures were compared to separate and recover lignocellulosic components from grape stalks. The first method consisted of mild acid hydrolysis for hemicelluloses separation, followed by an alkaline/oxidative step for lignin solubilization, while in the second method the acid hydrolysis was preceded by an alkali steeping phase. Influence of the length of the first step of both methods (from 2 to 24 h) on monosaccharides and cellulose yields was investigated. The first method allowed a higher sugar recovery for longer times, and a slightly lower amount of cellulose. Cellulose residues from both the methods were comparable for cellulose content and thermal profile (studied by differential scanning calorimetry). Acid hydrolysis of the first step was carried out also in autoclave, showing that xylan degradation could be described by a first order kinetics where at higher temperature the presence of a fast reaction and a slow reacting fraction must be accounted for.     

Oak wood hemicelluloses extracted with aqueous-alcoholic media

Hemicellulose fractions were isolated from oak wood ethanol extracts (40–90%). To determine the composition of these fractions, they were hydrolyzed and the hydrolysis products in the form of trimethylsilyl derivatives were analyzed by GLC/MS. Depending on the content of the ethanol, hemicelluloses of a different composition were extracted from wood. In alcohols that were kept in oak wood, intended for manufacturing brandy and whisky, the content of the hemicelluloses increased depending on the duration of storage. It is assumed that this makes drinks more full-bodied and makes them softer.     

Extraction of water-soluble hemicelluloses from barley husks

Heat treatment of barley husks was performed to extract arabinoxylan with high yield and high weight-averaged molecular mass (M(W)). Microwave irradiation was employed for initial screening of suitable residence times (2-15 min), temperatures (120-210 degrees C) and initial pH (3-13) of the reaction slurry. Microwave irradiation was shown to be a good method for predicting the effects of heat treatment on a larger scale using steam pretreatment. A M(W) of about 40,000 Da was achieved without the addition of chemicals, by both microwave irradiation and steam pretreatment, with a yield of about 9%. The yield was significantly increased by slightly increasing the severity factor. However, the M(W) decreased below 20,000 Da at severity factors above 3.7. Arabinosyl side groups were enzymatically hydrolysed from the arabinoxylan by alpha-L-arabinofuranosidase to a degree of 47%, demonstrating the ability to specifically alter the side group substitution of arabinoxylans with the use of enzymes.     

DMSO-soluble hemicelluloses from the husk of Sorghum grain

The chlorite holotellulose from the grain husk of Sorghum bicolor was extracted with DMSO and the hemicellulosic material separated into water-solu     

Alkali solubility of hemicelluloses in relation to delignification

The polysaccharide composition of bark from Pinus radiata, Salix fragilis, and Populus euramericana has been determined. All the barks contained lower levels of cellulose and hemicellulose than the corresponding woods; cellulose: hemicellulose ratios were also lower in the barks. Alkali extracted all of the hemicellulose-A but only half of the hemicellulose-B from P. radiata bark without prior delignification. Similar alkaline extraction removed almost all of the hemicellulose (A + B) from ryegrass leaves without delignification. With the other samples tested only a part of the hemicellulose A and B is extracted without delignification. It is suggested that the polysaccharide so extracted represents wall hemicellulose which is not linked to lignin or other wall constituents by alkali-stable links.     

Effects of auxin on the structure of hemicelluloses of Avene coleoptiles

Avena coleoptile hemicelluloses were fractionated into water-solublehemicelluloses I and IIB and water-insoluble hemicellulose IIA.These hemicelluloses were then subjected to glycosidic linkageanalysis by methylation technique, which revealed that hemicelluloseI was predominantly composed of arabinoxylans and ß-(l4)glucans and hemicellulose IIB was composed of arabinoxylans,ß-(l4) : (l3)-mixed linked glucans, ß-(l4)-glucansand xyloglucans. Hemicellulose IIA was mainly composed of xyloglucansand probably ß-(l4)-glucans. Methylation analysisof hemicelluloses extracted from Avena coleoptile segments treatedwith auxin in the presence of mannitol (0.15 M) indicated thatauxin apparently had no effect on the structure of arabinoxylanand caused a specific decrease in the amount of ß-(l4): (l3)-mixed linked glucan. (Received November 19, 1979; )     

透明圈法快速筛选半纤维素分解菌

半纤维素是植物性材料的重要组成成分之一 ,占 1 5 - 30 %,是陆生植物细胞壁的一种主要组分 ,较集中于初级和次级细胞壁中。半纤维素是由己糖和戊糖组成的异质多糖[1] 。微生物产生的半纤维素酶可降解半纤维素生成木糖及其它少量单糖 ,研究半纤维素生物转化具有重要意义 ,如在生物制浆 ,转化半纤维素为单糖、酒精 ,处理造纸厂废水的环境污染等方面具有广阔的应用前景 ,国外已有不少的研究者对降解半纤维素的真菌和细菌进行了研究[2 ] 。近年来 ,国内陆续出现了 7篇有关降解半纤维素真菌的研究报道 ,降解半纤维素细菌的报道只有 1篇[3 ] ,从…     

Seed storage hemicelluloses as wet-end additives in papermaking

Xyloglucans and galactomannans are examples of hemicelluloses that can be accumulated in seeds of many plants, being extensively studied and used for industrial applications. Guar gum and starch are polysaccharides currently used as wet-end additives in papermaking, whereas xyloglucans have never been reported to improve paper quality. In this work we show that different types of xyloglucans improved the mechanical properties of paper sheets without affecting the optical ones. Addition of 1% (w/w) of hemicelluloses to cellulosic pulp was able to increase by about 30% the mechanical properties such as burst and tear indexes. Seeds of several species could be used as source for the production of wet-end additives, since the results did not vary with the source of polysaccharides. Even if the utilisation of these hemicelluloses will not cost less than starch or guar gum, it might represent an important strategy for sustainable use of rainforest species.