甜菜纤维的制备及其性质

甜菜纤维的制备及其性质樊志和周人纲王占武李晓芝韩炜（河北省农林科学院农业物理生理生化研究所,石家庄０５００５１）Ａｐｒａｃｔｉｃａｌｐｒｅｐａｒａｔｉｏｎａｎｄｃｈａｒａｃｔｅｒｉｚａｔｉｏｎｏｆｄｉｅｔａｒｙｆｉｂｅｒｆｒｏｍｓｕｇａｒ┐ｂｅｅｔｐ...     

甜菜渣纤维素乙醇研究进展与展望

纤维素乙醇具有清洁、安全、可再生等优点,是新能源发展的重要方向,受到各国政府、企业的广泛关注。论文首先介绍了甜菜生物学特性,随后重点阐述甜菜及其副产物甜菜渣在三代生物乙醇开发中的优越性及应用进展。在此基础上提出了甜菜渣纤维素转化乙醇及组分分离综合利用的研究思路,认为甜菜渣将会作为一种重要原料在纤维素乙醇开发中发挥作用。     

Anaerobic biodegradation of sugar beet pulp

Sugar beet pulp is a by-product of sugar production and consists mainly of cellulose, hemicellulose and pectin. Its composition is suitable for biological degradation. A possible alternative for the utilization of this material (besides cattle feeding) can be anaerobic methanogenic degradation. It has an additional advantage – biogas production. Beet pulp was treated by a two-step anaerobic process. The first step consisted of hydrolysis andacidification. The second step was methanogenesis. In this paper, observation ofthe process of anaerobic degradation and determination of optimal parameters is discussed. A laboratory-scale model for sugar beet pulp anaerobic biodegradation was operated. Results of model performance have shown very good pulp digestion characteristics. In addition, high efficiency removal of organic matter was achieved. Methane yield was over 0.360 m³ kg^-1 dried pulp and excess sludge production was 0.094 g per gram COD added.     

Application of cellulase and pectinase from fungal origin for the liquefaction and saccharification of biomass

Commercial cellulase [see 1,4-(1,3;1,4)-β-d-glucan 4-glucanohydrolase, EC 3.2.1.4] from Trichoderma viride and pectinase [poly(1,4-α-d-galacturonide) glycanohydrolase, EC 3.2.1.15] from Aspergillus niger have been applied to produce fermentation syrups from sugar-beet pulp and potato fibre. Cellulosic, hemicellulosic and pectic polysaccharides of these substrates were hydrolysed extensively. Recovery of enzymes has been investigated in a packed-column reactor, connected with a hollow-fibre ultrafiltration unit. Enzymes appeared to be stable in this type of reactor, although part of the enzyme activity was lost, especially by adsorption onto the substrate residue.     

Effect of dietary fibre on nitrogen retention and fibre associated threonine losses in growing pigs

Apart from being an energy source, dietary fibre is also discussed to act as anti-nutritional factor reducing apparent precaecal protein and amino acid (AA) digestibility due to reduced absorption or increased endogenous secretion or both. However, the amounts of protein and AA of endogenous origin determined at the terminal ileum in cannulated animals do not represent the total losses associated with endogenous secretion. A high proportion of secreted protein is reabsorbed and does not reach the terminal ileum, and losses occur during synthesis of endogenous protein. Therefore, the present study used an alternative indirect approach, taking the reduction of nitrogen (N) retention in a threonine (Thr) limited diet as a sensitive indicator for fibre-associated Thr losses. Two experiments were conducted with 12 castrated male pigs each between 37 and 75 kg body weight to measure the effect of the intake of Thr and 150 and 300 g/d fibre from wheat bran (Exp. 1), or 150 g/d fibre from rape seed, cassava leaves, and cassava root peels, respectively (Exp. 2), on N retention. During two (Exp. 1) and three (Exp. 2) balance periods the animals were subjected to the dietary treatments according to a cross-over design. All animals received 1350 g/d of a wheat–soybean-based diet supplemented with free AA to ensure Thr being the first-limiting AA. To determine the effect of Thr on N retention, intake of the basal diet was reduced to 1150 g/d and supplemented with corn starch to reach equal energy intake and an unchanged AA pattern. With increasing BW additional starch was added to all diets to ensure a constant energy intake of 1.25 MJ ME/kg BW^0.75. Since the fibre sources contained small amounts of Thr, N retentions were corrected for precaecal digestible Thr intake originating from the fibre sources according to the Thr effect on N retention as determined in experiment 1. Corrected N retentions were affected by fibre level (p = 0.007) and source (p < 0.001). Fibre-associated Thr losses amounted to 3.3, 3.2, 1.2, and 1.1 g/kg fibre from wheat bran, rapeseed, cassava leaf, and cassava root peel, respectively. It is concluded that Thr losses per gram of dietary fibre depend on the fibre source and that fibre concentration and source in pig diets should be considered as a factor affecting Thr requirement.     

Control of the larvae ofConorhynchus mendicus (Col.: curculionidae) bySteinernema carpocapsae andSteinernema feltiae (nematoda,steinernematidae) in the gharb area (Morocco)

Two entomopathogenic nematodes,Steirnernema carpocapsae andS. feltiae were evaluated in the laboratory and under field conditions against larvae ofConorhynchus mendicus, a pest of sugar beet in the Gharb area of Morocco. Nematodes were applied in an artificially infested field using a knapsack sprayer either during the day or in the evening after sunset. The number of insect cadavers recovered from both soil and sugar beet plants was greater in the treated plots compared with the untreated ones. The percent reduction in live larvae was significantly greater in theS. carpocapsae treated plots (89.5% and 59.5% for night an day application respectively) compared with those treated withS. feltiae (68.5% and 28% respectively). The efficacy of entomopathogenic nematodes was therefore increased by application at night particularly in the case ofS. carpocapsae where control was maintained for 45 days.     

Addition of citrus pulp and apple pomace in diets for dogs: influence on fermentation kinetics,digestion, faecal characteristics and bacterial populations

Fermentation kinetics, digestibility, faecal characteristics and bacterial populations (aerobes, anaerobes, lactobacilli, lactic acid bacteria, enterococci, coliforms and clostridia) of dog food mixed with citrus pulp and apple pomace were evaluated. The in vitro gas production of a pre-digested dog food mixed with 0, 30, 50 and 70 g/kg dry matter (DM) of citrus pulp or apple pomace was measured, and also an experiment with dogs fed the same dog food with or without the addition of 70 g/kg of either fresh citrus pulp or apple pomace was conducted. Gas production increased linearly (p < 0.001) and quadratically (p < 0.001) as fibre levels augmented. The inclusion of fibre sources in the diets resulted in higher faecal output (p = 0.005) and defecation frequency (p < 0.001), and lower faecal pH (p < 0.001) and digestibility values (p < 0.01). Faecal consistencies and microbial populations did not differ among treatments. The addition of fresh citrus and apple was effective to stimulate the hindgut fermentation, but slightly depressed the digestion.     

Effects of a dietary organic acid mixture and of dietary fibre levels on ileal and faecal nutrient apparent digestibility, bacterial nitrogen flow, microbial metabolite concentrations and rate of passage in the digestive tract of pigs

Six 34-kg barrows were fitted with a post-valve T-caecum cannula and assigned to six dietary treatments according to a 6 × 5 change-over design to study how a mixture of formic acid, sorbate, and benzoate (0 or 8.4 g/kg feed) influences apparent ileal and faecal digestibility coefficients, bacterial nitrogen (N) flow, microbial metabolite concentrations, and passage rate in pigs fed isoenergetic diets with medium, high, or very high fibre content (neutral-detergent fibre (NDF): 199, 224, and 248 g/kg dry matter, respectively). These barley and soya-bean meal based diets contained 0, 75, and 150 g/kg barley fibre (NDF: 577 g/kg) and 0, 8, and 16 g/kg rapeseed oil, respectively. The dietary organic acid mixture improved the apparent ileal digestibility of 14 of the 17 amino acids analysed (P < 0.05). Increasing levels of dietary fibre linearly decreased the apparent ileal digestibility of six of the 17 amino acids analysed (P < 0.05). Ileal flows of bacterial N and amino acids as assessed on the basis of purine flow were decreased by the dietary organic acid mixture (P < 0.05) but were not affected by dietary fibre level (P>0.05). As assessed on the basis of diaminopimelic acid flow, bacterial N flow was increased by both the dietary organic acid mixture and increased dietary fibre levels (P < 0.05). The dietary organic acid mixture reduced the concentration of lactic acid and increased that of acetic acid in ileal digesta (P < 0.05), while dietary fibre levels had a quadratic effect on concentrations of acetic, propionic, and butyric acid (P < 0.05). The mean retention time of Co (solute marker) and Yb (particle marker) in the large intestine decreased in a linear manner by increasing dietary fibre levels (P < 0.05) but was not affected by the dietary organic acid mixture (P>0.05). The results show that a dietary organic acid mixture has a positive effect on the apparent ileal digestibility of most amino acids irrespective of dietary fibre levels. This could be at least partly related to changes in bacterial N flow in the ileum. However, different bacterial markers showed opposite effects on bacterial N flow, which makes it questionable to use a constant bacterial marker / bacterial N ratio to estimate bacterial N flow. Increasing levels of dietary fibre had negative effects on the apparent ileal amino acid digestibilities and shortened the mean retention time of digesta in the large intestine.     

Some preliminary results on the action of rhamnogalacturonase on rhamnogalacturonan oligosaccharides from beet pulp

Sugar-beet pulp was saponified and then hydrolysed with 0.1 M HCI at 80°C for 72 h, and a rhamnogalacturonan fraction was isolated by ion-exchange chromatography on AG 1X8 resin. Four individual oligomers, and a mixture of oligomers with higher degrees of polymerization, were obtained by chromatography on BioGel P-4. They all presented the -d-GalAp-(1 [→2)--l-Rhap-(1 → 4)--d-GalAp-(1]_n→2)-l-Rhap structure (with n 2) The five fractions were submitted to hydrolysis with rhamnogalacturonase. The enzyme was active on oligomers with degrees of polymerization f10, and gave as main products -l-Rhap-(1 → 4)--d-GalAp-(1 → 2)--l-Rhap(1 → 4)-d-GalAp and -d-GalAp-(1 → 2)--l- Rhap- (1 → 4) --d- GalAp- (1 → 2) --l-Rhap-(1 → 4)-d-GalAp.