Liquefaction of dulse (Palmaria palmata (L.) Kuntze) by a commercial enzyme preparation and a purified endo ,β-1,4-D-xylanase

Liquefaction of dry and freshPalmaria palmata by food grade enzyme preparations and a purified endo--1,4-D-xylanase was studied.The endo--1,4-D-xylanase (EC 3.2.1.8) was purified to homogeneity from a commercial food grade enzyme prepared fromAspergillus niger. It has a molecular weight of 22 500, a pI of 3.5, is inactive toward corn arabinoxylan,p-nitrophenyl--D-xylose, carboxymethyl cellulose but shows a weak activity toward microcrystalline cellulose. It hydrolyzes oat and dulse xylan equally well in seawater and deionized water essentially into xylose and xylobiose. It is stable between pH 5.5 to 9.0 and 0 to 30 °C and its activity is optimal at pH 4.5–5.5 and 40–60 °C. It has a K_m of 2.2 and 2.8 mg ml^-1 and V_max of 3600 and 3900 nkat mg^-1 of protein on oat and dulse xylan, respectively.Acetate buffer, deionized water and seawater alone extracted 62.6 to 64.5 % of the dry weight of dry dulse, but the use of commercial food grade enzyme preparations or the purified xylanase improved liquefaction to 81.2–87.1 %. Xylose and galactose were the only sugars present in the soluble extracts. Deionized and seawater extracted 58.8–52.7 and 39.1–42.2% of the dry weight of the fresh algae collected in fall and summer, respectively. Only galactose was found in the seawater extract, while some xylose with galactose were measured in the deionized water extract of the fresh autumn algal sample. Purified and crude xylanase improved liquefaction of fresh algae to 79.8–81.4 and 71.9–77.9% of the fresh dry weight (fall and summer, respectively) in deionized and seawater, respectively, and increased the xylose content of the soluble fractions. Polysaccharides in the soluble residues were composed of 1,3/1,4-linked xylose, 1-linked galactose (floridoside) and 1,4-linked glucose (cellulose) and contained essentially 1,4-linked xylose and 1,4-linked glucose in insoluble fractions obtained after enzymatic treatment.The use of xylanase-containing food grade enzyme preparations improves liquefaction ofPalmaria palmata, particularly from fresh alga. This study indicates that processing such as drying may modify markedly the solubility ofP. palmata cell wall polysaccharides, which would imply the existence of some organization and/or other components in the fresh cell wall that lower xylan solubility in seawater.     

THE COMPOSITION AND PHYLOGENETIC SIGNIFICANCE OF THE MOUGEOTIA (CHAROPHYCEAE) CELL WALL1

The two-layered, fibrillar cell wall of Mougeotia C. Agardh sp. consisted of 63.6% non-cellulosic carbohydrates and 13.4% cellulose. The orientation of cellulose microfibrils in the native cell wall agrees with the multinet growth hypothesis, which has been employed to explain the shift in microfibril orientation from transverse (inner wall) toward axial (outer wall). Monosaccharide analysis of isolated cell walls revealed the presence of ten sugars with glucose, xylose and galactose most abundant. Methylation analysis of the acid-modified, 1 N NaOH insoluble residue fraction showed that it was composed almost exclusively of 4-linked glucose, confirming the presence of cellulose. The major hemicellulosic carbohydrate was semi-purified by DEAE Sephacel (Cl^?) anion-exchange chromatography of the hot 1 N NaOH soluble fraction. This hemicellulose was a xylan consisting of a 4-xylosyl backbone and 2,4-xylosyl branch points. The major hot water soluble neutral polysaccharide was identified as a 3-linked galactan. Mougeotia cell wall composition is similar to that of (Charophyceae) and has homologies with vascular plant cell walls. Our observations support transtructural evidence which suggests that members of the Charophyceae represent the phylogenetic line that gave rise to vascular plants. Therefore, the primary cell walls of vascular plants many have evolved directly from structures typical of the filamentous green algal cell walls found in the Charophyceae.     

Atmospheric and room temperature plasma mutagenesis and astaxanthin production from sugarcane bagasse hydrolysate by Phaffia rhodozyma mutant Y1

In this study, atmospheric and room temperature plasma and ultraviolet mutagenesis was studied for astaxanthin overproducing mutant. Phaffia rhodozyma mutant Y1 was obtained from the selection plate with 120 μmol/L diphenylamine as selection agent, and its carotenoid concentration and content were 54.38 mg/L and 5.38 mg/g, which were 19.02 % and 21.20 % higher than that of the original strain, respectively. Sugarcane bagasse hydrolysate was used for astaxanthin production by mutant Y1 at 22 °C and 220 rpm for 96 h, and the biomass and carotenoid concentration reached 12.65 g/L and 88.57 mg/L, respectively. Ultrasonication and cellulase were used to break cell wall and the parameters were optimized, achieving an astaxanthin extraction rate of 96.01 %. The present work provided a novel combined mutagenesis method for astaxanthin overproducing mutant and a green cell wall disruption process for astaxanthin extraction, which would play a solid foundation on the development of natural astaxanthin.     

Production kinetics of β-carotene from Planococcus sp. TRC1 with concomitant bioconversion of industrial solid waste into crystalline cellulose rich biomass

Cost effective bioprocessing of nutraceuticals in present global scenario is a matter of concern. This study explored Paper mill sludge (PMS) and sugarcane bagasse (SCB) as inexpensive substrate for Planococcus sp. TRC1 mediated valuable β-carotene production and residual treated biomass as value added crystalline cellulose source simultaneously. Both biomass supported significant bacterial growth reaching highest yield 38.54 ± 1.4 mg/g on PMS (36 h) and 47.13 ± 1.9 mg/g (48 h) on SCB in solid state fermentation. Luedeking-Piret model revealed growth associated production with α and much lower β values of 5.18 and 0.24 for PMS and 4.5 and 0.165 for SCB. Cost analysis exhibited decrementation of pigment cost/mg by 84 % compared to synthetic media. Optimum production conditions were 30 °C temperature, pH 7, 10 % inoculum and initial moisture content 80 % (PMS) and 85 % (SCB). TLC (R_f = 0.9), HPLC (RT = 7.646) and lambda max (465 nm) confirmed pigment’s β-carotene nature with significant antioxidant and antimicrobial activity. It showed stability at varied temperature, pH and light conditions along with negligible phytotoxicity on Vigna radiata. Planococcus sp. TRC1 delignified PMS (41 %) and SCB (38 %) and FT-IR, FESEM and XRD suggested crystalline nature of residual cellulose rich fraction shedding light on a biorefinery approach for valorization of industrial solid wastes.     

北京市某社区女性居民膳食模式与常见慢性病的关系

目的：了解北京市某社区女性居民的主要膳食模式及与常见慢性病的关系。方法：于2018年5月--2019年2月,采用多阶段整群随机抽样的方式对辖区内460名18~70岁女性居民进行问卷调查。收集基本资料、饮食行为习惯、家族病史、慢病史、治疗史等情况,分析饮食行为对常见慢性病的影响。结果：北京市白纸坊社区女性居民共有4种主要膳食模式,分别为：“传统膳食模式”（占43.1%）、“以肉类为主膳食模式”（占27.9%）、“水果蛋奶膳食模式”（占16.4%）和“主食、酒类和饮料膳食模式”（占12.6%）。Logistic 回归分析提示：在控制混杂因素后,“以肉类为主膳食模式”和“主食、酒类和饮料膳食模式”与社区女性居民高血压呈正相关性（OR=1.314和1.995,P<0.05）。“传统膳食模式”和“主食、酒类和饮料膳食模式”与社区女性居民糖尿病呈正相关性（OR=1.239和1.332,P<0.05）。“以肉类为主膳食模式”和“主食、酒类和饮料膳食模式”与社区女性居民血脂异常呈正相关性（OR=1.902和1.557,P<0.05）。“以肉类为主膳食模式”与社区女性居民冠心病呈正相关性（OR=1.338,P<0.05）。结论：社区女性居民膳食模式构成存在一定的不合理,且与主要慢性病的发生相关,应控制相关影响因素,促进健康、合理的膳食模式,降低慢性病的发生。     

Determination of Mass Transfer Coefficients for A Mixture of Compost,Sugarcane Bagasse,and Granulated Activated Carbon as Packing Medium in Biofilter

ABSTRACT

A laboratory-scale biofilter unit packed with a mixture of compost, sugarcane bagasse, and granulated activated carbon (GAC) in the ratio of 55:30:15 by weight was used for a biofiltration study of air stream containing benzene, toluene, ethylbenzene, and o-xylene (BTEX). The effect of superficial velocity on mass transfer coefficient for the packing was studied by maintaining gas flow rates of 3, 4, 5, 6, and 8 L min^?1 for inlet concentrations of 0.1, 0.4, and 0.8 g m^?3 for each of benzene, toluene, ethylbenzene, and o-xylene. The maximum elimination capacity was found to be 20.92, 22.72, 20.73, and 18.94 g m^?3 h^?1 for BTEX, respectively, for stated flow rates. Removal efficiency of BTEX decreased from 99% to 71% for increasing inlet concentration from 0.1 to 0.8 g m^?3. Gas film mass transfer coefficient predicted by modified Onda's equation was within ±10% of the experimental values.     

Cleavage of Disulfide Bonds of Wheat Glutenin by Mercuric Chloride

The dissociation of wheat glutenin into subunits was observed by treatment with a small amount of mercuric chloride under moderate conditions, suggesting that the cleavage of inter-polypeptide chain disulfide bonds in the glutenin might occur. The dissociation into the subunits was examined by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The electrophoretic patterns of the glutenin treated with mercuric chloride were essentially similar to those of the glutenin treated with 2-mercaptoethanol. Silver nitrate also had the same effects as mercuric chloride, and p-chloromercuribenzoate and N-ethylmaleimide showed no effect on the dissociation of the glutenin. Complete dissociation was achieved when the glutenin solution containing 0.5% SDS and 0.01 m phosphate buffer (pH 7.0) was incubated with 10^?3 m mercuric chloride (about four moles per mole of disulfide groups) at 30°C for 20 hr. Partial dissociation was also observed after 30 min incubation. Increasing temperature and SDS concentration promoted the rate of the dissociation of the glutenin by mercuric chloride.     

Cloning,Sequencing, and Expression of the Gene Encoding an Intracellular β-D-Xylosidase from Streptomyces thermoviolaceus OPC-520

The intracellular β-xylosidase was induced when Streptomyces thermoviolaceus OPC-520 was grown at 50°C in a minimal medium containing xylan or xylooligosaccharides. The 82-kDa protein with β-xylosidase activity was partially purified and its N-terminal amino acid sequence was analyzed. The gene encoding the enzyme was cloned, sequenced, and expressed in Escherichia coli. The bxlA gene consists of a 2,100-bp open reading frame encoding 770 amino acids. The deduced amino acid sequence of the bxlA gene product had significant similarity with β-xylosidases classified into family 3 of glycosyl hydrolases. The bxlA gene was expressed in E. coli, and the recombinant protein was purified to homogeneity. The enzyme was a monomer with a molecular mass of 82 kDa. The purified enzyme showed hydrolytic activity towards only p-nitrophenyl-β-D-xylopyranoside among the synthetic glycosides tested. Thin-layer chromatography analysis showed that the enzyme is an exo-type enzyme that hydrolyze xylooligosaccharides, but had no activity toward xylan. High activity against pNPX occurred in the pH range 6.0-7.0 and temperature range 40-50°C.     

Optimization of fermentation medium for xylanase-producing strain Xw2

To improve the fermentation yield of xylanase by optimizing the fermentation conditions for strain Xw2, a Plackett-Burman design was used to evaluate the effects of eight variables on xylanase production by strain Xw2. The steepest ascent （descent） method was used to approach the optimal response surface experimental area. The optimal fermentation conditions were obtained by central composite design and response surface analysis. The results showed that the composition of the optimal fermentation medium was corn cob ＋ 1.5% wheat bran （1：1）, 0.04% MnSO4, 0.04% K2HPO4. 3H2O, and an inoculum size of 6% in 50 mL liquid volume （pH = 6.0）. The optimal culture conditions were 28oc at 150 r/min for 54.23 h. The results of this study can serve as the basis for the industrial production and application of xylanase.