声光动力联合杀菌技术对牡蛎的保鲜效果

针对单独光动力杀菌、声动力杀菌技术的缺陷,探究声光动力联合杀菌技术（Sono-photodynamic sterilization treatment,SPDT）对牡蛎的保鲜效果。该研究以牡蛎为研究对象,在以姜黄素浓度、声光动力处理时间及超声波功率为单因素试验的基础上进行正交试验,优化声光动力联合杀菌技术对牡蛎保鲜的工艺条件,同时对比不同处理前后的牡蛎进行理化指标及感官评分。结果表明：在姜黄素浓度50μmol/L、超声波功率600 W及声光动力处理时间60 min的条件下,对牡蛎的保鲜效果明显,菌落总数为4.52 lg (CFU/g)。此外,声光动力联合杀菌技术与空白对照组、姜黄素组、光照组、超声波组比较,较好维持牡蛎的pH值、硫代巴比妥酸和挥发性盐基氮在较低数值,保持了牡蛎的外观、硬度及色泽等感官品质,使牡蛎在4℃下贮藏货架期由6d延长至12d。因此,声光动力联合杀菌技术具有良好的杀菌特性,可用于生鲜牡蛎的保鲜,为声光动力联合杀菌技术应用于食品领域提供理论指导与技术参考。     

工厂化循环水养殖中臭氧/紫外线反应系统的水处理性能

为增强臭氧在水产应用的安全性,满足工厂化循环水养殖对有机物去除和水体消毒的需要,该文开发O3/UV反应系统。通过试验方法研究该系统臭氧投加溶解区适宜的臭氧投加流量和处理量的关系、紫外辐射剂量配比等工艺参数,及对水质净化效果和水体消毒灭菌效果的影响等。试验结果表明:1)在满足所需水中溶解臭氧浓度的条件下,采用较低臭氧进气流量和较高进水流量有利于提高系统的臭氧溶解率和利用率。该系统在水流量为5 m3/h,臭氧投加量为(8.78±0.60)g/h时可得到水中臭氧溶解质量浓度为1.53 mg/L的臭氧水,臭氧溶解率为82.7%,臭氧利用率为97.7%。2)增加紫外灯的功率和数量均可提高对臭氧的去除率,但增加紫外灯的数量对其性能提升效果更明显。该系统在紫外剂量为1 996 MJ/cm2,对残留臭氧的去除率为83.82%。3)该系统对紫外消光度、总有机碳、水色等指标的去除率相比单独使用臭氧分别提升109.95%、89.77%和51.44%,杀菌率可达97%以上,实现工厂化循环水养殖低臭氧残留条件下的有机物有效去除和消毒杀菌。     

高温处理与添加物料对蚓粪基质培育辣椒壮苗的影响

蚓粪是蚯蚓处理有机固体废弃物的产物,具备替代泥炭作为蔬菜育苗基质材料的优良性质。蚓粪高温处理（120℃）后加入蛭石、 尿素等物料复配成育苗基质,通过温室育苗和室内分析的手段,分析蚓粪中活性有机物和GA3、 IAA的含量变化以及蚓粪基质培育辣椒幼苗的系统发育特征。结果表明, 蚓粪高温处理过程增加了蚓粪中GA3含量,使活性有机物裂解成具有相同母核类极性更大的水溶性衍生物。无论是否高温处理,蚓粪育苗基质都有利于辣椒幼苗茎粗、 株高、 展宽、 叶片数、 根长、 根表面积、 根体积、 根尖数、 鲜（干）重和壮苗指数的提高,但会导致辣椒幼苗叶片叶绿素含量的减小。蚓粪添加蛭石和高温处理后育苗能够增大辣椒幼苗根直径。高温处理蚓粪中添加蛭石（蚓粪∶蛭石=4∶1,V∶V）和尿素（0.50 kg/m3）有利于提高辣椒幼苗成苗率,增加鲜干物质累积,促进茎叶和根系的系统发育,增大壮苗指数。可见,蚓粪高温处理后与蛭石按4∶1体积比均匀混合后用于辣椒育苗,最能提升辣椒幼苗的各项指标,形成壮苗。     

Sterilization of exopolysaccharides produced by deep-sea bacteria: impact on their stability and degradation

Polysaccharides are highly heat-sensitive macromolecules, so high temperature treatments are greatly destructive and cause considerable damage, such as a great decrease in both viscosity and molecular weight of the polymer. The technical feasibility of the production of exopolysaccharides by deep-sea bacteria Vibrio diabolicus and Alteromonas infernus was previously demonstrated using a bioproduct manufacturing process. The objective of this study was to determine which sterilization method, other than heat sterilization, was the most appropriate for these marine exopolysaccharides and was in accordance with bioprocess engineering requirements. Chemical sterilization using low-temperature ethylene oxide and a mixture of ionized gases (plasmas) was compared to the sterilization methods using gamma and beta radiations. The changes to both the physical and chemical properties of the sterilized exopolysaccharides were analyzed. The use of ethylene oxide can be recommended for the sterilization of polysaccharides as a weak effect on both rheological and structural properties was observed. This low-temperature gas sterilizing process is very efficient, giving a good Sterility Assurance Level (SAL), and is also well suited to large-scale compound manufacturing in the pharmaceutical industry.     

脱水鲜面物理杀菌工艺参数研究

研究半干面内菌落含量变化规律对延长产品货架期与提高面食品质具有重要意义。本文选用70℃-90℃温度,70%-90%相对湿度和5min-20min干燥时间三组工艺参数,采用干燥试验台进行杀菌试验,按照国家标准测定杀菌前后面条试样内菌落总数。结果表明：温度、湿度和干燥时间是影响菌落含量的重要参数;约80℃时温度对菌落总数的影响出现拐点,温度在70℃-80℃区间时菌落总数急剧降低,温度在80℃-90℃区间时菌落总数变化缓慢且菌落总数维持在约200CFU/g水平;菌落总数随相对湿度和干燥时间的延长逐级递减。     

赤子爱胜蚓(Eisenia fetida)对秸秆施入后土壤有机碳和微生物的影响

蚯蚓能够通过自身生命活动和对土著土壤生物的调控作用而直接或间接影响土壤活性有机碳的变化。为探索蚯蚓影响土壤有机碳变化的机理,在混入水稻秸秆的灭菌/未灭菌土壤中接种蚯蚓(Eisenia fetida),以不接种蚯蚓的处理为对照,比较30 d微宇宙培养后不同处理土壤有机碳含量及土壤微生物群落结构的变化。结果显示,接种蚯蚓增加了土壤微生物量碳(MBC)和CO2累积排放量,但仅在灭菌土壤中存在显著性差异。接种蚯蚓对土壤总有机碳(TOC)、活性有机碳(LOC)和可溶性有机碳(DOC)的影响则因土壤是否灭菌而异。末端限制性片段长度多样性(T-RFLP)分析显示,在灭菌土壤中接种蚯蚓获得了更多的末端片段(TRFs),而在未灭菌土壤中蚯蚓的存在并未明显改变TRFs的数量,且接种蚯蚓与无蚯蚓的处理共享了近50%的TRFs。冗余分析(RDA)显示土壤细菌群落结构因蚯蚓是否存在而不同,但仅在灭菌土壤中接种蚯蚓的处理同时与LOC、DOC、MBC和CO2累积排放量呈较好的正相关关系。因此认为,在该实验的灭菌土壤中,来源于蚯蚓肠道的微生物可能通过快速繁殖并成为优势种进而影响土壤有机碳的变化,但这一作用在未灭菌土壤中则有可能因为土壤土著微生物的竞争作用而被削弱。     

土壤灭菌和杀真菌剂对紫花苜蓿生长和重金属累积的影响

以云南会泽铅锌矿周边重金属污染的农田土壤为基质,开展室内盆栽试验,研究土壤灭菌和杀真菌剂(苯菌灵)对紫花苜蓿的生长、光合色素含量、部分抗氧化生理、重金属含量与累积量的影响。结果表明:土壤灭菌显著影响苜蓿的抗氧化生理,导致巯基含量减少54%,丙二醛含量增加44%;显著降低光合色素含量和植株的生长,叶绿素a、叶绿素b和类胡萝卜素含量分别下降27%、23%和30%,株高降低45%,地上部和地下部生物量分别减少74%和85%;土壤灭菌和施用苯菌灵均显著增加土壤有效Pb含量和苜蓿地下部Pb的含量,减少苜蓿地下部Zn的含量;土壤灭菌还显著增加苜蓿地上部Cd的含量;土壤灭菌极显著减少苜蓿对重金属的累积,植株Pb、Zn、Cd和Cu的累积量分别下降74%、78%、68%和76%;施用苯菌灵对苜蓿生长、抗氧化生理及重金属累积的影响均不显著。总之,完全消除土壤微生物明显降低了苜蓿对重金属的耐性与累积能力,土壤微生物对植物耐受重金属有重要作用。     

Antioxidant and antiproliferative activities of heated sterilized pepsin hydrolysate derived from half-fin anchovy (Setipinna taty)

In this paper we studied the antioxidant and antiproliferative activities of the heated pepsin hydrolysate from a marine fish half-fin anchovy (HAHp-H). Furthermore, we compared the chemical profiles including the amino acid composition, the browning intensity, the IR and UV-visible spectra, and the molecular weight distribution between the half-fin anchovy pepsin hydrolysate (HAHp) and HAHp-H. Results showed that heat sterilization on HAHp improved the 1,1-diphenyl-2-picryl-hydrazil (DPPH) radical-scavenging activity and reducing power. In addition, the antiproliferative activities were all increased for HAHp-H on DU-145 human prostate cancer cell line, 1299 human lung cancer cell line and 109 human esophagus cancer cell line. The contents of free amino acid and reducing sugar of HAHp-H were decreased (P < 0.05). However, hydrophobic amino acid residues and the browning intensity of HAHp-H were increased. FT-IR spectroscopy indicated that amide I and amide III bands of HAHp-H were slightly modified, whereas band intensity of amide II was reduced dramatically. Thermal sterilization resulted in the increased fractions of HAHp-H with molecular weight of 3000-5000 Da and below 500 Da. The enhanced antioxidant and antiproliferative activities of HAHp-H might be attributed to the Maillard reaction.     

Depressed gross mineralization and immobilization of nitrogen and changes in microbial population in soil after heat treatment

Partial sterilization causes a change in N mineralization in soil. An increase in the net rate of N mineralization was reported in soil with chloropicrin applied to it (Rovira 1976), and has been well known in soil fumigated with chloroform to measure the microbial biomass N (Jenkinson and Ladd 1981). The gross rate of N mineralization increased in soil inoculated with fresh soil following fumigation with chloroform (Shen et al. 1984). The increased rate of N mineralization has been attributed to the rapid decomposition of organisms killed by partial sterilization (Jenkinson 1966). On the other hand, Nira et al. (1996) reported that the application of a fumigant in a field depressed the gross rates of N mineralization and immobilization in spite of the increase in the net rate of N mineralization. These results suggested that the increase in the net rate of N mineralization by partial sterilization is presumably due to the change in the ratio of N mineralization to immobilization. However, the residues of a fumigant may depress gross N transformation in the field, because the residues may continue to influence microbial activity long after the original treatment (Jenkinson 1966). Some effects of partial sterilization without residues on gross N mineralization remain to be determined.     

Properties and metabolic diversity of microbial communities in soils treated with steam sterilization compared with methyl bromide and chloropicrin fumigations

The effects of steam sterilization (SS) on soil microbial properties including metabolic diversity of the microbial communities were examined in a greenhouse compared with those of two fumigants, methyl bromide (MB) and chloropicrin (CP). The numbers of fungi decreased in all the treatments. Nitrifiers, both ammonium-oxidizing bacteria and nitrite-oxidizing bacteria, were severely affected by the SS and CP treatments, resulting in their virtual disappearance. The decrease in the levels of microbial biomass C and N after the treatments suggested that the SS and CP treatments eradicated the microorganisms more effectively than the MB treatment and that the influence of the former persisted until the end of the experiment, 4 months after the treatments. Accumulation of NH₄-N was observed after the SS and CP treatments mainly due to the partial decomposition of the dead microorganisms and the marked decrease in the number of ammonium-oxidizing bacteria. The richness and average well color development (AWCD) values in the microbial communities after the SS treatment were evaluated by the carbon substrate utilization method using Biolog ECO MicroPlates. The values decreased markedly immediately after the treatment but showed a rapid recovery, while those after the CP treatment continued to decrease until the transplanting of tomato seedlings. The effect of the MB treatment on the soil microbial communities was less pronounced. The growth of the tomato plants was promoted by the SS and CP treatments due to the increase in the N supply at the initial stage of tomato growth.