日本落叶松硫酸盐法制浆特性

以日本落叶松为原料,分别研究了用碱量、硫化度、保温时间对硫酸盐法制浆的影响,并对不同树龄、不同部位和不同单株之间的制浆差别进行了比较.结果发现,最佳蒸煮工艺条件为:用碱量21%、硫化度25%、最高温度170℃,保温时间2.5 h;随着树龄的增大,日本落叶松的蒸煮难度增加;树干的顶部、干部和基部相比较,干部原料较易蒸煮;不同单株间的制浆性能差别较小;12年生日本落叶松纸浆的物理性能较15年生、23年生树龄的好.     

不同生长期绿洲一号和巨菌草制浆性能探讨

采用超声辅助预处理及蒸煮对1年、2年和3年不同生长期的绿洲一号及巨菌草的制浆性能进行了评价。结果表明,在相同制浆工艺条件下(超声波预处理用碱量4%,硫化度2%,超声时间2 h;蒸煮用碱量6%,硫化度0,固液比1∶4,最高温度170℃,保温时间1 h),3年生巨菌草较适合作为制浆原料,其制浆的粗浆得率49.3%,卡伯值14.5,纸浆黏度850.63 mL/g,白度39.3%。超声波预处理液中木素含量4.3 g/L,还原糖含量2.9 g/L,蒸煮黑液中木素含量2.9 g/L,还原糖含量5.7 g/L。抄造纸张抗张指数56.4 N·m/g,撕裂指数20.5 mN·m~2/g,耐破指数2.35 kPa·m~2/g。     

H因子对混合阔叶木硫酸盐制浆性能的影响

对混合阔叶木进行了不同H因子下硫酸盐制浆性能探讨,并优化了硫酸盐制浆工艺条件.结果表明:混合阔叶木较佳制浆条件为蒸煮H因子不低于800、用碱量16%～20%、蒸煮温度165℃,此条件下,纸浆得率和卡伯值较理想,蒸煮结果较好.蒸煮H因子900、用碱量16%、蒸煮温度165℃时,纸浆得率达最高值44.27%,纸浆强度性能指标较好,裂断长高达8.18km、耐破指数4.81kPa·m2/g、撕裂指数12.7mN·m2/g.但纸浆白度仅为25.8%,卡伯值26.4.高H因子和低用碱量的制浆工艺,可得到较高强度性能指标的纸浆.     

生物酶预处理改善麦草氧碱制浆性能的研究

以麦草为原料,经生物酶（脂肪酶、木聚糖酶、二者的复合酶）预处理后,采用碳酸钠氧碱制浆工艺制备麦草生物化学浆,研究生物酶预处理对麦草纤维形貌、纸浆纤维形态及纸浆成纸物理性能的影响。结果表明,经复合酶预处理后,麦草浆卡伯值为13.08、纸浆成纸白度可达40.9% ISO,较未经酶预处理的纸浆分别低1.34、高6.8% ISO;经碳酸钠氧碱制浆工艺制备的纸浆细小纤维含量明显下降,成纸抗张指数可达97.4 N?m/g,较未经酶预处理的纸浆成纸抗张指数（86.2 N?m/g）提高了12.9%,生物酶预处理可明显改善麦草的生物化学制浆性能。     

楸树枝桠材硫酸盐法制浆的研究

对楸树3个无性系的两类径级枝桠材的硫酸盐化学法制浆及造纸性能进行了研究.研究结果表明:粗、细枝桠材硫酸盐法蒸煮最佳用碱量分别为21%和22%(以Na2O计).在此条件下蒸煮,可获得卡伯值为2l、纸浆得率分别为41%和34%的未漂化学浆.在相同的蒸煮工艺条件下,两类径级的楸树枝桠材硫酸盐法制浆性能表现出明显的差异.楸树3个无性系枝桠材硫酸盐法制浆性能差别不十分明显,在相同蒸煮条件下所得纸浆的卡伯值、纸浆得率和筛渣率相近.8401枝桠材硫酸盐浆相对较难漂白,8402和金丝楸硫酸盐浆的可漂性相对较好.     

碱抽提对蔗渣碱性过氧化氢法制浆的影响

探讨了碱抽提对碱性过氧化氢法制浆的影响,并检测浆的强度性能。实验结果表明:在碱性过氧化氢法蒸煮之前,用浓度40 g/L的氢氧化钠溶液在25℃下抽提1 h,得到的纸浆卡伯值为7.19、黏度为16.85 mPa·s、细浆得率为57.02%、白度为47.17%ISO,相较于未抽提的纸浆卡伯值降低了9.8%,白度提高了1.0%;纸张抗张指数为85.32 N·m/g、撕裂指数3.01 mN·m~2/g、耐破指数4.43 kPa·m~2/g,相较于未抽提的纸浆抗张指数提高了8.04%,耐破指数提高了7.79%。     

不同树龄四倍体刺槐SFP-AQ制浆性能研究

四倍体刺槐作为一种新的速生树种,是造纸工业潜在的纤维资源。本文对四倍体幼龄刺槐(2-4年)进行了材性分析,采用SFP-AQ(碱性亚硫酸钠甲醛-蒽醌法)制浆,通过正交试验,确定其较优的蒸煮工艺条件:四倍体刺槐两年生用碱量(以Na2O计)18%~20%,亚硫酸化度35%~45%,一次升温时间110~130min,二次升温时间50~60min;四倍体刺槐四年生用碱量(以Na2O计)19%~22%,亚硫酸化度45%~50%,一次升温时间:110~130min,二次升温时间:40~50min。最高蒸煮温度为160-165℃,液比1∶5.5。Na2CO3用量2.3%,AQ用量0.05%,甲醛用量2.5%。两年生四倍体刺槐在49.0°SR附近,纸浆各项物理性能指标较好,抗张指数74.6N.m/g,撕裂指数17.07mN.m2/g,耐折度290次,紧度0.48g/cm3。四年生四倍体刺槐在41.5°SR附近,纸浆具有较好的物理性能,抗张指数70.9N.m/g,撕裂指数19.55mN.m2/g,耐折度270次,紧度0.49g/cm3。总的来说,四倍体刺槐比较适合SPF-AQ法制浆。     

稻草低温p-TsOH制浆性能研究

对稻草进行对甲苯磺酸(p-TsOH)一步法制浆和两步法制浆,并与碱法制浆进行对比,探讨了p-TsOH法制浆的可行性。结果表明,与碱法稻草浆相比,p-TsOH稻草浆的得率更高,成纸的松厚度及强度更好;p-TsOH两步法制浆可以进一步提高木质素脱除率,且浆料纤维断裂少,平均纤维长度更长。其中,稀碱-p-TsOH两步法制浆(N-P45T70t60)比p-TsOH一步法制浆(P45T70t60)的木质素脱除率高12.7个百分点,成纸的抗张指数和耐破指数分别高4.52 N·m/g和0.653 kPa·m~2/g,耐破指数与碱法稻草浆成纸相当。     

改良杂交尾细桉材性特征随树龄变化及APMP制浆性能分析

本文主要研究了人工改良杂交尾细桉LH1和天然杂交尾细桉U6的基本密度、化学组分、纤维形态随树龄的变化趋势及APMP制浆性能分析。结果表明,两种桉木的基本密度、综纤维素含量、纤维长度、纤维宽度及长宽比随树龄呈增加趋势,灰分含量、1%NaOH抽出物含量随树龄呈下降趋势。两种桉木纤维长度在0.6-0.8mm之间,长宽比在34.4~42.4之间,小于45,属于短纤维原料。改良后LH1的基本密度、综纤维素含量、长宽比高于天然杂交尾细桉U6,利于制浆造纸。经相同条件制浆漂白后,250mL游离度的纸浆,LH1的抗张指数提高42.3%,耐破指数提高87.5%,撕裂指数提高49.5%。     

湿地松硫酸盐法一级与二级蒸煮的研究

进行了广东湿地松硫酸盐法一级与二级蒸煮的研究,对两种蒸煮结果作了比较。结果表明:广东湿地松的化学成份与马尾松相似,但其纤维平均长度比马尾松小;硫酸盐法蒸煮过程脱木素的规律与马尾松相同。采用活性碱浓度为139/l(Na_20计)的黑液进行第一级蒸煮后,加入低碱量白液进行第二级蒸煮的二级蒸煮法,可以提高纸浆的得率;第一级蒸煮采用高硫化度的黑液,可以提高木素的溶出率,降低纸浆的高锰酸钾值,若蒸煮到纸浆的高锰酸钾值相同,则用高硫化度黑液预蒸煮的纸浆得率比较高。广东湿地松纤维平均长度为2.96mm,浆张裂断长为6000米左右,耐破指数4.9—5.3kPa·m~2/g,撕裂指数19—22mN·m~2/g。     

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.     

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.     

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.     

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.     

Cloning and expression analysis of two catalase genes from Aspergillus oryzae

Fungi contain distinct genes encoding the same class of enzyme that are differentially regulated according to conditions. We cloned two catalase genes, catA and catB, from Aspergillus oryzae. The catA gene predicts a 747-amino-acid polypeptide sharing 81% identity with Aspergillus fumigatus catalase (catA) and 77% with Aspergillus nidulans catalase (catA). The catB gene predicts a 725-amino-acid polypeptide sharing 82% identity with A. fumigatus catalase (catB) and 75% with A. nidulans catalase (catB). However, the catA and catB genes share little homology (41%) with one another, suggesting that each gene belongs to a distinct gene family. Overexpression studies demonstrated that both genes encode a functional catalase. Promoter assays indicated that the catA gene is developmentally regulated as it was preferentially expressed in solid-state cultures undergoing sporulation. However, its expression was not affected by hydrogen peroxide treatment. Conversely, the catB gene was highly expressed under all culture conditions tested, and it was induced by hydrogen peroxide treatment. These results suggest that the catB gene may be mainly used for detoxification of oxidative stress while the catA gene may have another role such as chaperoning proteins in the spore.     

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.