酸性低共熔溶剂预处理制备含木质素的纤维素纳米纤丝及其复合膜的研究

采用酸性低共熔溶剂（deep eutectic solvent,DES）预处理并结合高压均质法制备了含木质素的纤维素纳米纤丝（lignin-containing cellulose nanofibril,LCNF）,并与聚乙烯醇（PVA）共混制备了LCNF/PVA复合膜,探讨了2种酸性DES预处理的效果,分析比较了LCNF的特性及LCNF/PVA复合膜的性能。结果表明,乳酸-氯化胆碱（LC）和乙酸-氯化胆碱（AC）对半纤维素的提取率均达到78%以上,其中LC预处理后用乙醇洗涤的处理方式对木质素的提取率高达61.2%;DES预处理后,乙醇洗涤有利于木质素的分离;利用LC制备的纤维素纳米纤丝（LC-E-LCNF）的直径为50～100 nm;相较于纯PVA膜,LCNF/PVA复合膜的疏水性明显提高,应力提升至70.3 MPa,紫外屏蔽性接近100%,且具有良好的热稳定性和雾度,以及一定的保鲜性能,该复合膜有望应用于食品包装领域。     

旧报纸基含木质素CNC和CNF的综合制备与表征

本研究以旧报纸为原料,采用硫酸水解法制备了含木质素纤维素纳米晶体（LCNC）,随后利用超声辅助球磨法将酸解沉淀的木质纤维素固体残渣（LCSR）解纤成含木质素纤维素纳米纤丝（LCNF）,实现了LCNC和LCNF的综合制备,综合产率高达85%以上。采用多种手段对LCNC和LCNF样品的结构特性进行分析表征。结果表明,LCNC呈棒状晶体结构,LCNF呈长丝状结构,木质素以球状颗粒存在于LCNC和LCNF中。LCNC平均长度和宽度分别为143.6和24.8 nm,LCNF的平均直径为16.2 nm。X射线衍射仪（XRD）结果显示LCNC和LCNF均保留纤维素I型结构,且木质素含量越高,其结晶度越低。同时,木质素本身的高疏水性和热稳定性使得木质素含量大的LCNC和LCNF具有更好的疏水性和热稳定性。     

聚乙烯吡咯烷酮及锂藻土对纤维素纳米结构纸的影响

在纤维素纳米结构纸（CNP）制备过程中,用聚乙烯吡咯烷酮（PVP）和锂藻土（Laponite）作为分散剂,以降低纤维素纳米纤维（CNF）分散体的黏度,提高其脱水速度,避免CNF的絮聚。结果表明,相比未添加PVP和锂藻土的CNP,添加0.4％（相对于CNF绝干质量,下同）PVP和0.3％锂藻土的CNP的脱水时间从135 min减少到48 min,透明度从82.0％提高到90.3％,同时密度降低了63.6%,平均粗糙度（Ra）和均方根粗糙度（Rq）分别降低了69.7%和69.1%。     

木质素含量对纤维素纳米纤维热稳定性的影响

分别采用热水、绿液及漂白预处理以改变蔗渣和云杉纤维素纳米纤维的木质素含量,探究残余木质素含量对纤维素纳米纤维热稳定性能的影响。结果表明,经过热水预处理制备的蔗渣和云杉纤维素纳米纤维的木质素含量分别比经过绿液预处理制备的蔗渣和云杉纤维素纳米纤维高16.1%和8.9%,比经过漂白预处理制备的蔗渣和云杉纤维素纳米纤维的高22.7%和24.3%,半纤维素含量相对较低。经过热水预处理制备的蔗渣和云杉纤维素纳米纤维的热稳定性分别比经过漂白预处理制备的蔗渣和云杉纤维素纳米纤维的热稳定性提高了约4.3%和5.4%。     

基于低共熔溶剂硫酸化改性的纤维素纳米纤丝的制备及性能分析

本研究以漂白杨木化学浆为原料,采用氨基磺酸与甘油基低共熔溶剂（DES）结合超微粉碎处理制备硫酸化纤维素纳米纤丝（CNF）。探讨了预处理时间（1.0、1.5 h）、氨基磺酸与纤维素的摩尔比（20∶1、15∶1、10∶1）对纸浆纤维质量和CNF性能的影响。利用纤维质量分析仪、元素分析仪和傅里叶变换红外光谱仪对DES预处理前后的纸浆纤维结构进行了分析表征。结果表明,与未经过DES预处理的纸浆相比,经过DES预处理后纸浆纤维长度显著降低,最多降低72.67%,而纸浆纤维直径有所增加,最大增加26.82%。随着预处理时间的延长和氨基磺酸用量的增加,纸浆纤维长度降低,纸浆纤维的直径增大,纸浆纤维的硫含量增加,取代度（DS）提高至0.17。使用粒度分析仪、原子力显微镜、Zeta电位检测仪、X射线衍射仪和多重光散射分析仪对制备的CNF进行分析显示,DES预处理后,CNF的平均粒径减小,平均粒径最小为40.02 nm,CNF胶体的Zeta电位在 -43.50~-18.80 mV之间,结晶度降低,最低为58.51%,CNF悬浮液的稳定性提高。     

全生物基三元DES预处理促进芦竹酶解机理研究

针对二元中性低共熔溶剂（DES）体系效率低的问题,构建新型全生物基三元DES（氯化胆碱/乙酰丙酸/1,4-丁二醇）体系,并用于芦竹（Arundo donax L.）预处理;采用成分分析、扫描电子显微镜（SEM）、X射线衍射仪（XRD）、傅里叶变换红外光谱仪（FT-IR）对预处理前后芦竹化学成分、结构及表面形貌变化等进行分析,结合复合动力学模型探究预处理促进芦竹酶解机理。结果表明,三元DES是高效的预处理体系,在140 ℃下处理3 h后,木质素和半纤维素的脱除率分别达46.4%和75.6%,残渣纤维素和聚木糖酶解率高达~100%和96.6%;建立的复合动力学模型可准确地描述三元DES预处理耦合酶解过程中葡萄糖和木糖变化行为（R² > 0.99）。由预处理温度升高引起的半纤维素和木质素高效脱除、纤维表面粗糙度增大及纤维素结晶结构破坏是促进芦竹酶解的主要原因。     

乙二醇抑制DES预处理过程中木质素缩合程度的研究

利用氯化胆碱/草酸和氯化胆碱/草酸/乙二醇2种低共熔溶剂（DES）体系预处理竹粉以分馏提取木质素,并通过多种表征手段探究木质素的结构变化。结果表明,在110 ℃反应180 min的条件下,氯化胆碱/草酸二元DES体系提取的木质素（二元DES木质素）中β-O-4芳基醚键的相对含量仅为0.26/Ar,氯化胆碱/乙二醇/草酸三元DES体系提取的木质素（三元DES木质素）此值则为0.43/Ar。同时,二元DES木质素中的缩合结构（β-β,β-5=3.11/Ar）及缩合的芳环C—C连接（Aromatic C—C=2.18/Ar）多于三元DES木质素（β-β,β-5=2.02/Ar,Aromatic C—C=1.99/Ar）。利用超声辅助三元DES体系预处理过程,发现反应20 min后木质素脱除率即可达76.0%。采用水相电位滴定法测定不同反应条件下的三元DES木质素的酚羟基和羧基含量;并提出乙二醇在三元DES体系预处理竹粉过程中抑制木质素缩合的机理,证实乙二醇与对香豆酸和阿魏酸反应生成了酯化的木质素结构。     

基于螺旋挤压-GVL/水/酸两步预处理的溶解浆联产糠醛和木质素

针对目前溶解浆生产过程中存在的半纤维素和木质素利用率低、溶解浆质量有待提升等问题,本研究基于螺旋挤压耦合γ-戊内酯（GVL）/水/酸预处理,提出绿色环保的溶解浆联产糠醛和木质素的工艺。结果表明,桉木经螺旋挤压-GVL/水/酸两步预处理（150 ℃下反应1.5 h）,蒸煮用碱量8%,漂白工艺OQP₁P₂,制备出α-纤维素含量为96.5%、白度为84.0%的高品质溶解浆;水解液分离木质素后,以甲基异丁基酮（MIBK）/H₂O-NaCl为催化体系,商业离子交换树脂为催化剂,于180 ℃下催化木糖水解液2 h,糠醛最大得率为96.0%;GVL木质素S/G比为4.81,保留一定含量的β-O-4键（22.6%）。经物料衡算,每100 g桉木可生产37.2 g溶解浆、6.2 g糠醛（理论值10.2 g）和16.4 g的GVL木质素。     

高透气性能CNF/环状拓扑形貌CNC复合薄膜的制备与性能研究

通过硫酸水解法及高强超声处理获得具有中空环状拓扑形貌的纤维素纳米晶体（RT-CNC）,并采用真空抽滤法制备了纤维素纳米纤丝（CNF）/RT-CNC薄膜。结果表明,RT-RNC的环壁宽度约为3.5 nm,长度为10～50 nm,具有明显中空特性,其成膜过程中化学结构并未改变且保持纤维素Ⅰ结晶结构;CNF/RT-CNC薄膜的透气度为6.70μm/(Pa·s),相较于CNF薄膜（2.50μm/(Pa·s)）提高了168%,且其热降解性能良好。     

对甲基苯磺酸水解-高压均质法制备多尺度木质纤维素纳米纤丝

以杨木化学机械浆为原料,采用对甲基苯磺酸水解-高压均质法制备木质纤维素纳米纤丝（LCNF）;研究对甲基苯磺酸水解过程中木质素脱除规律及残余木质素对LCNF微观形态、尺寸、结晶结构和热稳定性的影响。结果表明,对甲基苯磺酸水解能有效去除木质素,削弱纤维间结合力,有利于高压均质过程中的微纤丝解离分散。与纤维原料相比,LCNF的无定形区遭到破坏,结晶度由43.9%增至66.0%。通过酸水解可以调控残余木质素含量,进而控制高压均质后LCNF的平均宽度,实现多尺度LCNF的制备。LCNF的木质素含量越低,LCNF分散性越好、尺寸越均一。当残余木质素含量为4.89%时,LCNF平均宽度最小（10.6 nm）,最大热失重降解温度（Tmax）在350～360℃。     

Arsenic content of some edible mushroom species

The arsenic contents of 162 fruit body samples of 37 common edible mushroom taxa were analyzed. The samples were gathered from different habitats of Hungary (mainly from mountains) between 1984 and 1999. The arsenic content of the samples was measured by the inductively coupled plasma spectrometry method. Very low [lower than 0.05 mg/kg dry matter (DM)] concentrations were found in the samples of 13 taxa, while higher (or very high) contents were quantified in other common taxa (the highest arsenic content was recorded in the fruit body of Laccaria amethysthea at 146.9 mg/kg DM). The species of eight genera (Agaricus, Calvatia, Collybia, Laccaria, Langermannia, Lepista, Lycoperdon, Macrolepiota) belong to the so-called accumulating taxa, and this tendency is evident on all habitats. This arsenic accumulation capability is found in two orders of Basidiomycetes (Agaricales and Gasteromycetales), which is to say this phenomenon occurs in the families Agaricaceae, Tricholomataceae and Gasteromycetaceae. The accumulating taxa found all have a saprotrophic type of nutrition; arsenic accumulation is not detectable in xilophagous or in mycorrhizal species. The consumption of the accumulating species found has only a low toxicological risk for three reasons: the consumed fresh fruit bodies contain about a tenfold lower arsenic level than the dried ones, the majority of arsenic occurs not in poisonous inorganic, but in less dangerous (or not poisonous) organic forms, and the frequency of consumption is low.     

Organization and localization of the dnaA and dnaK gene regions on the multichromosomal genome of Burkholderia multivorans ATCC 17616

The Burkholderia multivorans strain ATCC 17616 carries three circular chromosomes with sizes of 3.4, 2.5, and 0.9 Mb. To reveal the distribution and organization of the genes for fundamental cell functions on the genome of this bacterium, the dnaA and dnaK gene regions of ATCC 17616 were cloned and characterized. The gene organization of the dnaA region was rnpA-rmpH-dnaA-dnaN-gyrB with a single consensus DnaA-binding box (TTATCCACA) between the rmpH and dnaA genes. This intergenic region, however, did not work as an autonomously replicating sequence in ATCC 17616. On the other hand, the gene organization of the dnaK region was grpE-orf1 (gene for thioredoxin homologue)-dnaK-dnaJ-pabB (gene for p-aminobenzoate synthetase component homologue). A putative heat-shock promoter that showed good homology to the sigma32-dependent promoter consensus sequence in Escherichia coli was found upstream of the grpE gene, suggesting that these five genes constitute an operon. In M9 succinate minimal medium the dnaJ mutant grew more slowly than the wild-type strain, indicating that this operon is functional. Pulsed-field gel electrophoresis and Southern blot analyses indicated that both the dnaA and dnaK gene regions exist as single copies on the 3.4 Mb chromosome.     

Susceptibility of stored product insects to high concentrations of ozone at different exposure intervals

Ozone is a highly reactive gas with insecticidal activity. Past studies have indicated that ozone technology has potential as a management tool to control insect pests in bulk grain storage facilities. The objective of this study was to determine the efficacy of short periods of exposure to high ozone concentrations to kill all life stages of red flour beetle (Tribolium castaneum (Herbst)) (Coleoptera: Tenebrionidae), and Indianmeal moth (Plodia interpunctella (Hübner)) (Lepidoptera: Pyralidae), adult maize weevil (Sitophilus zeamais (Motsch.)) (Coleoptera: Curculionidae) and adult rice weevil (S. oryzae (L)) (Coleoptera: Curculionidae). Insects were treated with six ozone concentrations between 50 and 1800 ppm. The specific objective was to determine minimal time needed to attain 100% mortality. The most ozone-tolerant stages of T. castaneum were pupae and eggs, which required a treatment of 180 min at 1800 ppm ozone to reach 100% mortality. Eggs of P. interpunctella also required 180 min at 1800 ppm ozone to reach 100% mortality. Ozone treatments of 1800 ppm for 120 min and 1800 ppm for 60 min were required to kill all adult S. zeamais and adult S. oryzae, respectively. The results indicate that high ozone concentrations reduce the treatment times significantly over previously described results. Our results also provide new baseline information about insect tolerance to ozone treatment.     

Contamination with storage fungi of human food from Cameroon

In a mycological study, a total of 95 human food samples were investigated to evaluate the incidence of fungal contamination in Cameroon by conventional identification method and partly confirmed by DNA sequencing. The isolated fungal spp. were further studied to determine their toxigenic potentials. The investigation revealed the predominance of Aspergillus and Penicillium with 96% of samples contaminated with at least one species of these fungi, whereas the incidence of co-contamination of samples was 85%. Aspergillus flavus and Aspergillus parasiticus (Flavi section) were the most predominant species contaminating mainly maize and peanuts. In addition, P. crustosum and P. polonicum were the most common contaminants belonging to the genus Penicillium. On the other hand, A. ochraceus (Circumdati section) registered a low incidence rate of 5%, including other members of the Aspergillus group. Other members of the genera Rhizopus and Alternaria spp. were also registered in the study. A majority of fungal strains of A. ochraceus, A. parasiticus, P. crustosum and P. polonicum isolated were toxigenic, producing the mycotoxins tested for, while none was detected in cultures of A. fumigatus. The high incidence rate of fungi contamination coupled with their potentials in producing mycotoxins gives a strong indication that the samples tested may likely be contaminated with various mycotoxins. There is need for further study to assess the incidence of mycotoxins contamination in similar food samples.     

Assessment of the microbiological safety of salad vegetables and sauces from kebab take-away restaurants in the United Kingdom

The purpose of this study was to establish the microbiological safety of salad vegetables and sauces served in kebab take-away restaurants. Comparison with published microbiological guidelines revealed that 4.7% of 1213 salad vegetable samples were of unsatisfactory microbiological quality due to Escherichia coli and/or Staphylococcus aureus levels at ≥10² cfu g⁻¹. Another 0.3% of salad samples were of unacceptable quality due to S. aureus at ≥10⁴ cfu g⁻¹ (2 samples) or the presence of Salmonella Kentucky (1 sample). Cucumber was the most contaminated salad vegetable with regards to unsatisfactory levels of E. coli (6.0%) or S. aureus (4.5%). Five percent of 1208 sauce samples were of unsatisfactory microbiological quality due to E. coli, S. aureus at ≥10² cfu g⁻¹ and/or Bacillus cereus and other Bacillus spp. at ≥10⁴ cfu g⁻¹. A further 0.6% of sauce samples were of unacceptable quality due to Bacillus spp. (Bacillus subtilis, Bacillus pumilus, Bacillus licheniformis) at ≥10⁵ cfu g⁻¹ or the presence of Salmonella Agbeni (1 sample). More samples of chilli sauce (8.7%) were of unsatisfactory or unacceptable microbiological quality than any other sauce types. The results emphasize the need for good hygiene practices in kebab take-away restaurants handling these types of ready-to-eat products.     

鸡源大肠埃希氏菌mcr-1基因携带及分析

目的 了解在农业农村部禁止使用多黏菌素作为动物促生长使用后四川部分地区鸡源大肠埃希氏菌（E.coli）mcr-1基因的携带情况,为制定进一步防控措施提供依据。方法 采集四川部分地区市场售卖点肉鸡直肠拭子,用含有多黏菌素（终浓度4 μg/mL）的EC肉汤增菌接种含多黏菌素（终浓度4 μg/mL）的麦康凯平板,挑取可疑菌落,采用PCR方法鉴定菌株并检测mcr-1基因;微量肉汤稀释法测定mcr-1基因阳性菌株对临床常见抗菌药物耐药情况。脉冲场凝胶电泳（PFGE）对mcr-1基因阳性菌株进行同源分析。耐药基因质粒结合实验验证mcr-1基因传播途径。结果 从70份肉鸡样本中的13份检出mcr-1基因阳性大肠埃希氏菌,检出率18.57%（13/70）,对实验的13种抗生素,除13株mcr-1阳性菌株对头孢西丁有12株敏感以外,对其他抗生素都表现出不同程度的耐药,其中四环素和甲氧苄啶/磺胺甲恶唑耐药率最高,达到了100%（13/13）;其次是氨苄西林和氯霉素,耐药率为84.62%（11/13）。PFGE显示13株mcr-1阳性大肠埃希氏菌分属13个不同的型别;质粒结合实验显示mcr-1基因能够通过质粒传播。结论 mcr-1基因在鸡大肠内大肠杆菌中检测率比较高,且鸡大肠中mcr-1阳性大肠埃希氏菌的耐药情况比较严重。     

Formation of cereulide and enterotoxins by Bacillus cereus in fermented African locust beans

Afitin, iru and sonru are three spontaneously fermented African locust bean Benin condiments. The fermentation processes are exothermic, with temperatures mostly being above 40 °C. A total of 19 predominant Bacillus cereus isolates from afitin, iru and sonru, were investigated. The enterotoxin genes nhe (A, B, C) were present in all 19 isolates, the hbl (A, C, D) in one (afitin), and the cytK gene in three isolates (afitin). Levels of cytotoxicity to Vero cells and NheA production in BHI-broth was within the range of known diarrheal outbreak strains. Autoclaved cooked African locust beans inoculated with emetic (cereulide producing) B. cereus Ba18H2/RIF supported growth at 25, 30 and 40 °C with highly different maximum cereulide productions of 6 ± 5, 97 ± 3 and 0.04 ± 0.02 μg/g beans, respectively (48 h). For non-autoclaved cooked beans inoculated with 2, 4 and 6 log₁₀B. cereus Ba18H2/RIF spores/g beans, cereulide production was 5 ± 4, 64 ± 8 and 69 ± 34 μg/g beans, respectively at 24 h, while it was 70 ± 43, 92 ± 53 and 99 ± 31 μg/g at 48 h of fermentation at 30 °C. Even though high toxin levels were observed, to date there are no known reports on diarrhea or vomiting due to the consumption or afitin, iru and sonru in Benin, which also according to the present study is likely to be expected from the low levels of cereulide produced at 40 °C.     

Microbial profiles of frozen trimmings and silver sides prepared at Indian buffalo meat packing plants

To assess microbiological quality of buffalo meat trimmings (TT = 114) and silver sides (SS = 41), samples were collected from four different Indian meat packing plants. The aim of this study was: (i) to evaluate standard plate count (SPC), psychrotrophic count (PTC), Enterococcus feacalis count (EFC), Staphylococcus aureus count (SAC) and Escherichia coli count (ECC) and the presence of Salmonella spp. and Listeria monocytogenes; and (ii) also to determine vero toxic E. coli (VTEC) by polymerase chain reaction (PCR). TT samples had significantly higher (P < 0.001) SPC, PTC, EFC, and SAC than SS, while across the meat types there was no difference (P > 0.05) in ECC. E. coli was recovered from 32.4% TT and 19.5% SS samples. The prevalence rate of Salmonella spp. and L. monocytogenes in TT was 1.75% and 0.87%, respectively. But no SS sample was found to be positive for any of these two pathogens. VTEC was found in 2.58% of all the tested samples. This finding suggests that TT contain higher microbes but only small numbers of pathogens of latent zoonotic importance. The present study confirmed the importance of maintaining good process hygiene at meat plants for microbiological status of buffalo meat.     

Antioxidant activities of citrus herbal product extracts

Total phenolic content, DPPH free radical-scavenging activity, hydrogen peroxide-scavenging activity, ferrous ion-chelating activity and ferric-reducing antioxidant power (FRAP) of four citrus herbal products, Citri Reticulatae Pericarpium (CRP), Citri Reticulatae Viride Pericarpium (CRVP), Aurantii Immaturus Fructus (AIF) and Aurantii Fructus (AF) extracts were determined. EC₅₀ values of DPPH radical-scavenging activities ranged from 0.1 mg/ml (AF) to 1.59 mg/ml (AIF). EC₅₀ values of hydrogen peroxide-scavenging activities ranged from 0.08 mg/ml (AF) to 0.9 mg/ml (CRP). EC₅₀ values of ferrous ion-chelating activities ranged from 0.8 mg/ml (AF) to 2.08 mg/ml (AIF). The differences in DPPH free radical-scavenging activity, hydrogen peroxide-scavenging activity, and ferrous ion-chelating activity of all citrus herbal product extracts were significant. AF had the highest antioxidant activity. In this study, citrus herbal product extracts did not have good reducing power.