棘孢曲霉固态发酵柚皮产柚苷酶的条件优化

【目的】以柚皮为原料,优化棘孢曲霉利用柑橘加工副产物固态发酵柚苷酶的条件。【方法】采用高效液相色谱法检测酶活力,通过单因素试验考察固水比、装样量、接种量、温度对柚苷酶发酵的影响,用正交试验优化发酵条件。【结果】单因素试验结果的显著性分析表明培养基的固水比、装样量和培养温度对柚苷酶产量有显著性影响,而接种量影响不显著;经正交试验确定的优化条件是：固水比1:1 (质量体积比),装样量5 g/250 mL三角瓶,温度为30 °C,接种1 mL孢子悬浮液,发酵8 d。在此优化条件下,柚苷酶酶活力为8.19 IU/g干物质,比初始培养基产柚苷酶活力提高7.38倍。【结论】通过对固水比、装样量和发酵温度进行优化,大幅度提高了棘孢曲霉固态发酵柑橘加工副产物的柚苷酶产量,为柚苷酶的生产提供了一种高产发酵工艺。     

沙田柚系列遗传关系的RAPD标记研究

采用 RAPD标记技术分析了沙田柚系列 1 2个样品的遗传关系。利用经筛选具多态性的 1 4个 1 0碱基随机引物对 1 2个样品进行 DNA随机扩增 ,获得清晰可重复的位点 99个 ,其中多态性位点 5 8个 ,占 5 8.89% ;在部分样品中检出了特异性 RAPD标记 1 9个 ,占 1 9.1 9% ;通过样品间遗传相似性系数比较与 UPGMA聚类分析 ,并根据历史事实可知 ,广西沙田柚、梅州金柚为沙田柚的无性繁殖系 ,软枝系沙田柚、沙田柚早熟单株为沙田柚的芽变后代 ,梅花早柚、菊花心沙田柚、冬瓜圈沙田柚、段氏柚、垫江沙田柚、古老钱沙田柚为沙田柚的实生变异品系。     

不同时期深施重肥对沙田柚生长结果的影响

比较了夏季深施重肥与冬季深施重肥对沙田柚春梢、根系生长及产量、果实品质、叶片与土壤营养含量的影响。结果表明,夏季深施重肥可在一定程度上提高沙田柚叶片钙、铁、硼、全氮、全磷、全钾、0~40cm土壤速效磷与有机质含量,以及20~40cm土壤的全氮、速效钾和pH值,为根系的生长创造良好的土壤环境条件,进而提高叶片三要素的含量,显著促进新根和春梢的生长;夏季深施重肥的单株产量、单果重量与果实品质与冬季深施重肥间无显著差异。     

龙柚果肉糖积累与蔗糖代谢相关酶活性的研究

本文探讨龙柚果实发育过程中果肉糖积累与蔗糖代谢相关酶活性的变化。结果表明,在龙柚果实发育过程中,3种可溶性糖含量同步上升,在果实膨大期和成熟期,以蔗糖积累为主。在龙柚糖积累过程中,蔗糖合成酶(SS)和蔗糖磷酸合成酶(SPS)活性较高;而蔗糖中性转化酶(NI)活性则随着蔗糖的积累而降低。     

CPPU提高柚树苗抗旱性的研究

水分胁迫下,柚树苗叶片RWC、ψw、Pn及可溶性蛋白质,叶绿素含量下降,游离脯氨酸、MDA含量及SOD活性升高,CAT活性先上升后下降,APX活性、AsA和GSH含量明显下降,抗旱性强的品种具有较高的活性氧清除能力。CPPU处理提高柚树苗叶片RWC、Pn、叶绿素、游离脯氨酸、AsA、GSH含量,并增加SOD、APX活性,降低MDA水平,从而提高柚树苗抗旱性。实验结果表明,CPPU处理提高叶片对膜脂过氧化作用的保护能力可能是其提高柚树苗抗旱性的原因。     

Evaluation of Pomelo Seed Extracts as Natural Antioxidant,Antibacterial, Herbicidal Agents,and Their Functional Components

Pomelo seeds (PS) are important by-product of pomelo fruits (Citrus grandis Osbeck). The value-added utilization of PS remains highly challenged. This study aimed to investigate the utilization potential of PS as natural antioxidant, antibacterial, herbicidal agents, and their functional components. The ethanolic extract (EE) of PS and its four fractions as PEE (petroleum ether extract), AcOEtE (ethyl acetate extract), BTE (butanol extract), and WE (water extract), were prepared and biologically evaluated. BTE exhibited the best antioxidant activity among all these extracts, in both ABTS (2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt) and FRAP (ferric reducing antioxidant power) assays. AcOEtE was superior to other extracts in herbicidal assay against both Festuca elata Keng (IC₅₀ of 0.48 mg mL⁻¹) and Amaranthus retroflexus L. (IC₅₀ of 0.94 mg mL⁻¹). Meanwhile, both AcOEtE and BTE demonstrated inhibitory effects against Bacillus subtilis, Escherichia coli, and Xanthomonas citri subsp. citri, with MIC ranging 2.5–5.0 mg mL⁻¹. Furthermore, the primary chemical components involving naringin, deacetylnomilin, limonin, nomilin, and obacunone, were quantified in all these extracts. PCA (principal component analysis) suggested that naringin might highly contribute to the antioxidant activity of PS, and the herbicidal activity should be ascribed to limonoids. This study successfully identified AcOEtE and BTE as naturally occurring antioxidant, antibacterial, and herbicidal agents, showing application potential in food and cosmetics industries, and organic farming agriculture.     

柚类品种遗传相互关系的RAPD标记研究

利用22个经筛选在样品间具多态性的10碱基随机引物,对柚 [Citrus max ima (Burm.) Merr.] 的主要品种及柚的一个野生近缘种云南红河橙 (C. hongh eensisY. M. et al.)、一个栽培近缘种葡萄柚 (C. × paradisi Macfad) 共79个样品的总DNA进行PCR扩增.在样品间共产生164条RAPD标记带,其中多态性带134条,多态性百分率为81.71%;以NTSYS-pc (Version 1.80)软件计算样品间的Jaccard遗传相似系数,并进行UPGMA聚类分析.结果表明野生近缘种云南红河橙及栽培近缘种葡萄柚与柚三个种种内聚合良好,种间分异明显,为柚分类上的地位奠定了遗传学基础.特异性RAPD分子标记的研究为柚类品种的鉴定提供了重要指标.     

不同贮藏条件对沙田柚果实苦味物质含量的影响

沙田柚原产广西,营养丰富且适合高血压和糖尿病等患者食用,近年来在沙田柚产业中存在品质下降、有苦味、异味生成等问题。为了研究不同贮藏条件下沙田柚苦味物质的含量变化,该文利用高效液相色谱仪,对室温包薄膜袋(A)、室温不包薄膜袋(B)和4℃低温不包薄膜袋(C)三种不同贮藏条件下,沙田柚外果皮、中果皮、囊衣、汁胞和种子中柚皮苷、柠檬苦素和诺米林在贮藏过程中的含量变化进行了测定。结果表明：沙田柚果实苦味物质以柚皮苷为主,主要分布在中果皮和囊衣中,柠檬苦素主要分布在种子和外果皮中,诺米林主要分布在种子中。各处理果实在贮藏过程中苦味物质含量变化不同,其中柚皮苷含量略有上升,柠檬苦素和诺米林含量整体呈下降趋势,略有波动,而汁胞中柠檬苦素和诺米林含量先上升再下降。三种不同贮藏条件相比,4℃低温不包薄膜袋贮藏的果实汁胞中柚皮苷和柠檬苦素的含量最高,在贮藏第30天,A、B、C 三种不同贮藏条件果实汁胞中柚皮苷含量分别为(0.139±0.006)、(0.190±0.009)和(0.194±0.019) mg?g-1,柠檬苦素含量分别为(47.28±1.91)、(33.64±1.90)和(84.19±5.56)μg?g-1。与此相反,外果皮、中果皮、囊衣和种子中柚皮苷、柠檬苦素和诺米林含量最低。该研究结果为采后沙田柚贮藏保鲜方式的选择提供了理论指导。     

A sheathing mycorrhiza between the tropical bolete Phlebopus spongiosus and Citrus maxima

Phlebopus (Ph.) spongiosus was recently described from several pomelo orchards (Citrus maxima) in southern Vietnam. This fungus was suspected to associate with pomelo plants as an ectomycorrhiza, although members of the genus Phlebopus have previously been presumed saprotrophic. To clarify this association, pomelo roots collected from the orchard (in situ roots), and those cultured with Ph. spongiosus (in vitro roots) in test tubes for 12 wk, were examined for ectomycorrhizal colonization. Both in vitro and in situ roots were analyzed for colonization using fungal LSU nuclear ribosomal DNA sequencing. The in situ roots exhibited the anatomical features of ectomycorrhizae: a thick fungal mantle, Hartig net, and extramatrical hyphae. The Hartig net, however, was very rare and showed discontinuous development. The in vitro association between Ph. spongiosus and C. maxima showed ectomycorrhiza-like structures, i.e., mantles and rhizomorphs in the plant roots, but no Hartig net development in the roots. Continuous hyphal penetration was restricted to the exodermis in both in situ and in vitro roots. Although the association between Ph. spongiosus and C. maxima could be considered ectomycorrhizal, its anatomy matches the unique feature known as sheathing mycorrhiza.     

土壤施镁矫治琯溪蜜柚缺镁的研究

本文探讨钙镁磷和硫酸镁的三种土壤施用量对矫治盛果期琯溪蜜柚缺镁的效应。试验结果表明,两种镁肥的土壤施用,对提高土壤有效镁和植株镁含量以及改善土壤和植株钾、钙与镁之间的平衡有一定的作用,从而不同程度地矫治了缺镁,并促进植林的生长与结果。试验结果还表明,施用钙镁磷的效果优于硫酸镁。作者推荐,盛果期每年株施钙镁磷1.5～2.0kg较为适宜。