Physiological and chemotaxonomical studies on microflora within a composter operated at high temperature

Physiological and chemotaxonomical studies were carried out on microorganisms isolated from a composter operated at around 50 to 60 degrees C. Only gram-positive rods were isolated and the microbial counts on agar plates were relatively low (10(3) to 10(5) cfu/g-sample). The chemotaxonomic properties of the ten isolates revealed that they were typical of the genus Bacillus. Identification by the Biolog system concurred with the chemotaxonomy; all the strains were determined to be Bacillus. 16S rDNA analysis closely identified five of the isolates as B. licheniformis, one as B. subtilis, and two as B. thermoamylovorans, while the remaining two strains seemed to belong to a new species. However, in several cases 16S rDNA analysis and the Biolog system gave different results at the species level. The stability of microflora within the composter was also investigated using the Biolog system. Analysis of colonies obtained during three sampling periods--December 1997, April 1998, and June 1998--showed that the microflora in the composter remained fairly stable.     

Effects of C N ratio and pH of raw materials on oil degradation efficiency in a compost fermentation process

Waste oil treatment was attempted using a compost fermentation process. To develop a simple method for waste oil treatment, cheap and simple materials were used as compost materials. The fermentation experiment was performed using a domestic composter to determine the optimum conditions of the fermentation. Adjustment of the pH value during the compost fermentation was also important for progression of the oil degradation. When the pH value was not controlled, the pH value decreased quickly and reached about 2 and the oil degradation was stopped. Adding caustic lime to the raw materials caused the pH value of the compost to stabilize at approximately 7. The addition of a nitrogen source had a large effect on oil degradation during the compost fermentation. The optimum value of the C N ratio of the raw materials with pH control was between 10 and 40. When the C N ratio of the materials was adjusted to 10, 20, and 40, the rate constants for oil degradation were very similar. The rate constants for NH4+ consumption were also similar. Oil degradation efficiency reached 83.5% relative to the initial oil content in the compost materials. Repeated batch operation of the compost fermentation was carried out and the compost system could maintain good efficiency for oil degradation over several repeated batch operations. Finally, the compost system was applied to the treatment of recalled mayonnaise, with favorable results being obtained.     

Isolation and characterization of predominant microorganisms during decomposition of waste materials in a field-scale composter

A self-heating field-scale composter treating agro-industrial wastes within a period of 30 d was analyzed by denaturing gradient gel electrophoresis (DGGE) (Pedro et al., J. Biosci. Bioeng., 91, 159-165, 2001). Three major bands were derived from Propionibacterium acnes, Methylobacterium mesophilicum or M. radiotolerans, and Bacillus thermocloacae. Strains MSP09A and MSP06G with close affiliation to P. acnes and B. thermocloacae, respectively, were successfully isolated. Based on quantitative-PCR results, the relative population of MSP09A increased towards the end of the composting process (mesophilic stage) while MSP06G seemed to predominate during the middle period (thermophilic stage). These results correlated highly with their growth temperatures. MSP09A and MSP06G had different metabolic profiles which were largely affected by culture conditions. MSP09A was able to utilize large complex molecules of lipids and proteins. An interspecies relationship in terms of metabolites such as propionic acid was expected between the two microorganisms.     

Denaturing gradient gel electrophoresis analyses of microbial community from field-scale composter

The diversity of microbial community during the decomposition of waste in a field-scale composter (Hazaka system) was investigated by denaturing gradient gel electrophoresis (DGGE). The composter operates at a high temperature through a self-heating system, creating a thermophilic (60-76 degrees C) stage during the initial phase and a mesophilic (45 degrees C) stage towards the later phase of the composting period. The pH of the system (pH 7.75-8.10) did not vary significantly during the process while moisture content was reduced from 48.8% to 25.1%. DGGE and 16S rDNA analyses showed that the following genera were found throughout the process: Propionibacterium sp., Methylobacterium sp., Pseudomonas sp., and Bradyrhizobium sp. Different Bacillus spp. thrive at the thermophilic or the mesophilic stage while Clostridium sp. was only found at the initial phase of the process. Staphylococcus sp. and Caulobacter sp. or Brevundimonas sp. existed during the later phase of the composting period.     

Effect of methanol and water contents on production of biodiesel fuel from plant oil catalyzed by various lipases in a solvent-free system

Methyl esters synthesized from plant oil and methanol by the methanolysis reaction are potentially important as a biodiesel fuel. The methanolysis of soybean oil by lipases from various microorganisms was investigated. Several of the lipases were found to catalyze methanolysis in a water-containing system without an organic solvent. The lipases from Candida rugosa, Pseudomonas cepacia, and Pseudomonas fluorescens displayed particularly high catalytic ability. The reaction rates of methanolysis catalyzed by the C. rugosa and P. fluorescens lipases decreased significantly when the water content was low, showing that water prevents the inactivation of these lipases by methanol. On the other hand, the methanolysis reaction rate catalyzed by the P. cepacia lipase remained high even under a low water content. In addition, the P. cepacia lipase gave high methyl ester contents in the reaction mixture up to 2 or 3 molar equivalents of methanol to oil, which is attributed to the P. cepacia lipase having substantial methanol resistance. For the same methanol content, the reaction rates of methanolysis catalyzed by the P. cepacia lipase increased with decreasing water content, and hence lipases strongly resistant to high methanol, such as that from P. cepacia, are desirable for use in methanolysis reaction processes.     

Oxidative stability of fish oil enriched drinking yoghurt

The oxidative stability of fish oil enriched drinking yoghurt as well as the antioxidative effect of citric acid ester, vitamin K and disodium ethylenediaminetetraacetic acid (EDTA) were investigated by measuring peroxide value and volatile secondary oxidation products and by sensory analysis. No oxidation was observed in yoghurt stored at 2 °C for up to 19 days, with or without addition of citric acid ester. Fish oil enriched yoghurt was also very stable even when compared to yoghurt with added rapeseed oil or a mixture of rapeseed oil and fish oil stored for up to 29 days. The addition of 50 μm iron to yoghurt did not promote oxidation. The results obtained may indicate an antioxidative effect of EDTA and pro-oxidative effect of vitamin K. All yoghurts had similar viscosity and droplet size. In summary, fish oil enriched drinking yoghurt is very stable towards oxidation.     

Effect of acidification and oil on the thermal resistance of Bacillus stearothermophilus spores heated in food substrate

The effect of the addition of vinegar and/or oil to a food homogenate (tomato sauce, tuna and vegetables) on the thermal resistance of Bacillus stearothermophilus spores was studied. The results indicated that the food substrate without the addition of vinegar and oil and a pH value of 5.28 reduced the thermal resistance of B. stearothermophilus spores compared with that obtained in double-distilled water, (D121 = 1.41 and 3.08 min respectively). The addition of vinegar reduced the pH of the substrate (4.81) and consequently the D values were reduced (D121 = 1.28 min). The addition of soya oil and vinegar to substrate until a pH of 4.81, further reduced the thermal resistance of the spores, giving a D121 value of 0.93 min.     

Effect of gamma irradiation on microorganisms and components in empty fruit bunch and palm press fibre of oil palm wastes

The effects of irradiation on microbiological load and chemical components of empty fruit bunch (EFB) and palm press fibre (PPF) were investigated as the preliminary study for upgrading of oil palm wastes to animal feeds by fermentation. The initial contamination of microorganisms in both EFB and PPF was very high and there is no significant difference between the samples collected from various palm oil mills. The dose required to eliminate below the detectable level was more than 15 kGy for total aerobic bacteria, but 5–6 kGy is enough for fungi. The contents of holocellulose and lignin were c 60% and 25%, respectively, in both EFB and PPF, and the change in components by irradiation was small. EFB and PPF have a high water holding capacity suggesting that they are suitable substrates for fermentation. These results show that the irradiation by 5–10 kGy on EFB and PPF is applicable for the pasteurisation of fermentation media without any significant change in components.     

Production of recycled manure solids for use as bedding in Canadian dairy farms: II. Composting methods

Recent technological advances in the dairy industry have enabled Canadian farms with liquid manure systems to use mechanical solid-liquid separation paired with composting of the separated solids for on-farm production of low-cost bedding material. However, because several approaches are available, it is difficult for farmers to select the appropriate one to achieve high quality recycled manure solids (RMS). Whereas 3 solid-liquid manure separators were compared in part I of the series (companion paper in this issue), the present study (part II) aims to assess the performance of 4 composting methods (static or turned windrow and drum composter for 24 or 72 h) under laboratory conditions. Parameters evaluated included temperature, physico-chemical characteristics, and bacterial composition of RMS, as well as airborne microorganisms, dust, and gases associated with composting RMS. Because each treatment attained the desired composting temperature range of 40 to 65°C (either in heaps or in the drum composter), reductions in bacteria were a better indicator of the sanitation efficiency. The treatment of fresh RMS in a drum composter for 24 h showed decreased bacterial counts, especially for Escherichia coli (from 1.0 × 10⁵ to 2.0 × 10¹ cfu/g of dry matter) and Klebsiella spp. (from 3.2 × 10⁴ to 4.0 × 10² cfu/g of dry matter). Increasing the time spent in the rotating vessel to 72 h did not result in further decreases of these pathogens. Composting in a static or turned windrow achieved similar E. coli and Klebsiella spp. reductions as the 24-h drum composting but in 5 or 10 d, and generally showed the lowest occupational exposure risk for dairy farmers regarding concentrations of airborne mesophilic bacteria, mesophilic and thermotolerant fungi, and total dust. Drum-composted RMS stored in piles exhibited intermediate to high risk. Composting approaches did not have a major influence on the physico-chemical characteristics of RMS and gas emissions. Drum composting for 24 h was the best compromise in terms of product quality, temperature reached, decreased bacterial numbers, and emitted airborne contaminants. However, because levels of pathogenic agents rapidly increase once composted RMS are spread in stalls, bacteriological characteristics of RMS along with milk quality and animal health and welfare features should be monitored in Canadian dairy barns applying recommended separation (part I) and composting (part II) systems to evaluate health risk and optimize management practices.     

Chemical Composition,Antioxidant, and Antibacterial Activities of the Essential Oil and Methanol Extracts of Eucalyptus oleosa Leaves

This study was designed to examine the chemical composition of essential oil and in vitro antioxidant and antibacterial activity of the essential oil and methanol extracts of Eucalyptus oleosa F. Muell. The chemical composition of the hydrodistilled essential oil of the leaves of E. oleosa was analyzed by gas chromatography and gas chromatography/mass spectrometry. The main constituents of the oil were found to be 1,8-cineole (45.1%), α-pinene (14.52%), and α-terpineol (4.35%). The essential oil showed strong antibacterial activity against the test microorganisms studied, while polar subfraction of methanol extract had moderate antibacterial activity and the nonpolar subfraction of methanol extract did not show any antibacterial activity. In contrast, the extract showed much better activity than the essential oil in antioxidant activity assays employed, e.g., in DPPH systems, the highest radical-scavenging activity was shown by the polar subfraction (15.1 ± 0.7 μg/ml). In the second case, the inhibition capacity (%) of the nonpolar subfraction (98.2% ± 1.5) was found to be the stronger one. In addition, the amounts of total phenol components in the polar subfraction (186.3 ± 2.1 μg/mg) and the nonpolar subfraction (79.6 ± 1.4) were determined.     

植物甾醇在大豆油脂储藏过程中抗氧化作用的研究

研究了不同含量植物甾醇对一级大豆油储藏稳定性的影响。将不同甾醇添加量（0%、0.05%、0.075%、0.1%、0.15%、0.2%,w/w）的大豆油分别在45、25 oC避光条件下进行储藏试验,测定大豆油在储藏过程中品质指标的变化。结果表明,45 oC避光条件下,甾醇的添加量不超过0.1%,随着甾醇浓度的增加,大豆油抗氧化作用显著增大（P < 0.05）;而甾醇的添加量大于0.1%时,抗氧化作用减弱。25 oC避光条件下,添加植物甾醇能显著增强大豆油抗氧化的作用（P < 0.05）;随着甾醇浓度的增加,抗氧化作用有增大的效果;甾醇的添加量达到一定程度时,抗氧化作用不再随甾醇浓度增加而变大;甾醇在大豆油储藏过程中具有抗氧化作用,存在显著的量效关系。     

Chemical composition,antioxidative capacity and interactive antimicrobial potency of Satureja khuzestanica Jamzad essential oil and antimicrobial agents against selected food‐related microorganisms

This study aimed to determine the chemical composition, antimicrobial and antioxidative activity of Satureja khuzestanica Jamzad essential oil. The oil was analysed by GC and GC/MS. Twenty‐eight constituents were identified. The oxygenated monoterpenes (78.22%) were the principal compound group. Among them, carvacrol (53.86%) and thymol (19.84%) were the most abundant constituents. The oil exhibited an acceptable antimicrobial activity against most of the tested microorganisms. The checkerboard method was applied to determine fractional inhibitory concentration indices (FICIs) to interpret the synergetic, additive, indifference or antagonistic interactions between essential oil and each of antimicrobials (lysozyme, ciprofloxacin, fluconazole and amphotericin B) against food‐related microorganisms. The synergetic phenomenon (FICI ≤ 0.5) was observed in majority of combinations with the exception of the essential oil and lysozyme. The oil exhibited good 1,1‐diphenyl‐2‐picrylhydrazyl radical scavenging activity (IC₅₀ = 28.71 μg mL^?1). Also, the oil had strong antioxidative activity in β‐carotene‐linoleic acid assay relative antioxidant activity (RAA% = 95.45). This study demonstrated that the essential oil has beneficial biological properties and its simultaneous application with standard antimicrobials against food‐related microorganisms result in reduction in inhibitory doses of the antimicrobials in vitro.     

Effect of preservatives, tween 20, oil content and emulsion structure on the survival of Lactobacillus fructivorans in model salad dressings

The effect of potassium sorbate (PS), nisin, Tween^® 20 and oil level on the survival of Lactobacillus fructivorans in model salad dressings was studied. In general, L. fructivorans growth was prevented in formulated emulsions, but the addition of nisin was necessary to inactivate the bacterium throughout the storage time evaluated. The bacteriocin activity showed to be strongly dependent on system composition. Addition of PS alone did not influence L. fructivorans survival. But, when this preservative was added together with nisin to an emulsion containing 110 g/kg of oil, it exerted an antagonistic action on nisin effectiveness while for other levels of oil, a synergistic action was verified. The increase of oil level did not affect L. fructivorans survival in those emulsions without nisin. However, when the bacteriocin was present, it produced different effects which depended on system composition. Addition of tween did not affect L. fructivorans survival for emulsions free of additives or containing as preservative only PS. However, when nisin was present, the emulsifier effect was entirely dependant on oil content. Furthermore, the structure of the food matrix appeared as an additional factor which could influence either the growth of the microorganisms or the functionality of the preservatives. Tween addition turned the systems more fluid or solid, depending on the oil content of the systems considered. Results obtained highlight the importance of considering ingredient interactions when evaluating microbial stability of food systems.     

交东半岛艾蒿精油化学成分分析及其抗菌活性研究

对胶东半岛地区艾蒿的挥发油采用水蒸气蒸馏,索氏提取及超临界CO2三种方法提取,对其化学成分进行了研究,鉴定了31种活性物质,其中超临界CO2方法提取的艾蒿油活性成分种类和含量均高于水蒸气蒸馏法和索氏提取法。采用琼脂扩散法和微量肉汤稀释法对提取艾蒿油的抗菌活性进行了研究,以大肠杆菌、金黄色葡萄球菌和黄曲霉菌为供试菌种,结果表明上述三种提取方法所得艾蒿油对于所选的3种菌种均有良好的抗菌活性,尤对大肠杆菌抑制性最强,最低的抗菌浓度是0．1％（V／V）。     

Conventional and omics approaches shed light on Halitzia cheese,a long-forgotten white-brined cheese from Cyprus

Production and ripening of Halitzia cheese was examined by conventional physicochemical and microbiological analyses along with state-of-the art metagenomics. Cheese was made from (A) raw goat milk without the addition of starters; (B) pasteurised goat milk without the addition of starters; (C) pasteurised milk with the addition of starters. The type and counts of microorganisms were mainly influenced by ripening time; microbial counts for lactic acid bacteria were predominant and remained stable with little or no variation throughout ripening. Coliforms and coagulase positive staphylococci declined during ripening and at the end of ripening the staphylococci were not detected. Yeasts were detected at low counts but in great diversity throughout ripening. Metagenomics analysis confirmed the results obtained by the classical microbiological analysis. The physicochemical parameters during ripening were also determined; at 60 days the pH value and moisture, fat, protein, ash, and salt contents did not significantly differ amongst cheese types.     

胶东半岛艾蒿精油化学成分分析及其抗菌活性研究

对胶东半岛地区艾蒿的挥发油采用水蒸气蒸馏,索氏提取及超临界CO2三种方法提取,对其化学成分进行了研究,鉴定了31种活性物质,其中超临界CO2方法提取的艾蒿油活性成分种类和含量均高于水蒸气蒸馏法和索氏提取法。采用琼脂扩散法和微量肉汤稀释法对提取艾蒿油的抗菌活性进行了研究,以大肠杆菌、金黄色葡萄球菌和黄曲霉菌为供试菌种,结果表明上述三种提取方法所得艾蒿油对于所选的3种菌种均有良好的抗菌活性,尤对大肠杆菌抑制性最强,最低的抗菌浓度是0.1%(V/V)。     

大豆水溶性多糖的提取及其对酸性乳饮料的稳定作用

为了提高油菜籽油体乳液在不同环境条件下的稳定性。本文以带负电荷的可溶性大豆多糖（SSPS）和不带电荷的魔芋葡甘聚糖（KGM）为原料形成油菜籽油体乳液。利用激光粒度分析仪和显微镜分别对两种不同多糖的油菜籽油体乳液进行了粒度分析和微观结构观察,考察了两种含不同多糖的油菜籽油体乳液在不同环境应力（pH、离子浓度和热处理）下的稳定性,以不含多糖的油菜籽油体乳液作为对照。实验结果表明：油菜籽油体乳液的粒径随着SSPS和KGM浓度的增加逐渐减小。除了pH2.0,不含多糖的油菜籽油体乳液在不同pH的粒径都显著高于（P<0.05）含KGM和SSPS的油菜籽油体乳液的粒径,此外,除了pH10.0外,含SSPS的油菜籽油体乳液在不同pH的粒径显著低于（P<0.05）含KGM的油菜籽油体乳液的粒径,而且含SSPS的油菜籽油体乳液的粒径受pH的影响较小。不含多糖的油菜籽油体乳液在不同盐离子浓度时的粒径变化不显著（P>0.05）,但都显著高于（P<0.05）含KGM和SSPS的油菜籽油体乳液的粒径。微观结构图也显示了含KGM和SSPS的油菜籽油体乳液在不同盐离子浓度下其油滴的分散性要好于不含多糖的油菜籽油体乳液。不含多糖的油菜籽油体乳液的粒径随着温度的升高而逐渐增加,且都显著高于（P<0.05）含KGM和SSPS的油菜籽油体乳液的粒径,而含SSPS的油菜籽油体乳液的粒径受温度的影响不显著（P>0.05）。综合以上结果,KGM和SSPS都能显著提高油菜籽油体乳液的稳定性,且SSPS效果更好。

     

中药材对清香型白酒主要酿造微生物及风味物质的影响

为筛选可提升清香型白酒酿造质量的中药材,探究了20种中药材对发酵微生物酿酒酵母（Saccharomyces cerevisiae）Y1、异常威克汉姆酵母（Wickerhamomyces anomalus）Y29和米根霉（Rhizopus oryzae）G1生长的影响。于绿衣观音土曲中添加中药材,模拟清香型白酒工艺进行固态发酵小试实验,分析中药材的添加对糖化醅中微生物数量及清香型白酒原酒中主要风味物质的影响。结果表明,添加杏仁和甘草等中药材可促进菌株Y1和Y29的生长,添加桂皮、杏仁等中药材可促进菌株G1生长。添加丁香、红景天对菌株Y1、Y29和G1的抑制作用明显,其最适添加量为0.5 g/L。川芎、辣蓼和人参分别使糖化醅中细菌、酵母和霉菌增殖的效果最佳,其微生物增长率分别为143.03%、47.69%和73.47%。气相色谱表明,茴香使清香型白酒乙酸乙酯含量增加32.44%,茯苓使清香型白酒杂醇油含量降低9.23%。     

Biocatalysis and Biotransformation Producing γ-Decalactone

ABSTRACT: Geotrichum fragrans and another Geotrichum sp., 2 newly isolated microorganisms, produce -γ-decalactone, which exhibits odors characteristic of fruit and chocolate derivatives. The production of-γ-decalactone by Geotrichum species in broth, to which enzymatically hydrolyzed castor oil had been added, was investigated. The study of different microbial lipases, aimed at producing the best hydrolyzed oil for use as a precursor for the production of -γ-decalactone, was also studied. The addition of ricinoleic acid or hydrolyzed castor bean oil to the culture medium enhanced -γ-decalactone production. The greatest enhancement of -γ-decalactone production was noted, with a yield of 600 mg/L, when 5% of hydrolyzed castor bean oil was added to the medium and fermented by Geotrichum fragrans for 96 h.     

Ferulic acid production from clove oil by Pseudomonas fluorescens E118

For the production of the useful antioxidant ferulic acid from clove oil containing abundant eugenol, the growth of eugenol-degrading microorganisms in the presence of clove oil was examined. Pseudomonas fluorescens E118, a clove-oil-tolerant strain, accumulated 6.1 g/l ferulic acid under optimized culture conditions with the intermittent addition of eugenol. When the bacterium was applied to ferulic acid production from clove oil, 5.8 g/l ferulic acid was produced with the intermittent addition of clove oil. Since clove oil is much cheaper than eugenol, ferulic acid production from clove oil by the bacterium is promising for the industrial production of ferulic acid.