Effect of gelling agents and antibiotics on adventitious bud regeneration from In vitro leaves of pear

Summary The effect of the type of gelling agent and of several antibiotics on the adventitious bud regeneration from in vitro leaves was tested on eight pear genotypes. The use of gellan gum (Phytagel™) in the medium instead of agar had a very strong positive effect on the rate of adventitious bud regeneration for all pear genotypes tested in this study. This gelling agent induced faster cell divisions than agar, thus more callus was produced on wound sites and subsequently more buds regenerated. Incubation on gellan gum medium during the first 20 d of bud induction was sufficient to induce a stimulatory effect on regeneration and limited the production of hyperhydric buds. In the prospect of Agrobacterium transformation, the effect of several antibiotics was tested. Cefotaxime (200 mg/l) plus ticarcillin/clavulanic acid (100 mg/l) could be used in the culture medium without affecting the frequency of bud regeneration. The inhibition of bud regeneration was obtained with different kanamycin concentrations according to the gelling agent in the medium. On gellan gum medium, a concentration of 100 mg/l of kanamycin was suitable. These conditions can be recommended for experiments on Agrobacterium-mediated transformation of pear, where bacterial inoculation and presence of antibiotics generally reduce and delay bud regeneration.     

Preparation and in vitro evaluation of xanthan gum facilitated superabsorbent polymeric microspheres

Interpenetrating polymer network (IPN) hydrogel microspheres of xanthan gum (XG) based superabsorbent polymer (SAP) and poly(vinyl alcohol) (PVA) were prepared by water-in-oil (w/o) emulsion crosslinking method for sustained release of ciprofloxacin hydrochloride (CIPRO). The microspheres were prepared with various ratios of hydrolyzed SAP to PVA and extent of crosslinking density. The prepared microspheres with loose and rigid surfaces were evidenced by scanning electron microscope (SEM). Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis confirmed the IPN formation. Differential scanning calorimetry (DSC) study was performed to understand the dispersion nature of drug after encapsulation. The in vitro drug release study was extensively evaluated depending on the process variables in both acidic and alkaline media. All the formulations exhibited satisfactory physicochemical and in vitro release characteristics. Release data indicated a non-Fickian trend of drug release from the formulations. Based on the results, this study suggest that CIPRO loaded IPN microspheres were suitable for sustained release application.     

Constitutive expression of Vitreoscilla haemoglobin in Sphingomonas elodea to improve gellan gum production

Aims: To improve a commercially used strain for gellan production by exogenous Vitreoscilla haemoglobin (VHb). Methods and Results: VHb gene was expressed in Sphingomonas elodea under the control of constitutive bla promoter. Biochemical activity of expressed VHb was confirmed by CO‐difference spectra analysis that exhibited a characteristic absorption maximum at 419 nm. During cultivation, not only enhanced cell growth was detected, but also 20% improvement in gellan production was observed after 48 h of incubation, with a maximum yield of 16·82 g l^?1. Moreover, maximum sucrose conversion efficiency (g gellan per g sucrose) was 57·8, 20% higher than that of the parental strain. We further examined the polysaccharide production of VHb‐expressing strain at different aeration levels in Erlenmeyer flasks. Again, in all cases, a significant enhancement of gellan production was observed, and the enhancement was more significant under oxygen‐limiting conditions (up to 26·8%). Conclusions: VHb exhibited positive effect on cell growth and gellan yield of S. elodea, especially under hypoxic conditions. Significance and Impact of the Study: This is the first application of VHb as an effective metabolic engineering strategy in S. elodea to regulate cell growth and optimize gellan yield.     

不同施肥水平对益母草生长的影响

对益母草〔Ｌｅｏｎｕｒｕｓａｒｔｅｍｉｓｉａ（Ｌｏｕｒ．）Ｓ．Ｙ．Ｈｕ〕作不同肥料水平的田间处理,考评单株鲜重、地上部分鲜重、分蘖数和长叶速度等生物学特性。Ｌ４（２３）试验结果表明：（１）磷肥对益母草的单株鲜重、地上部分鲜重和分蘖数的影响起主导作用,氮肥次之,钾肥影响最弱;（２）对益母草的长叶速度,磷肥起决定性作用,氮肥、钾肥的影响不明显;（３）氮肥能促进叶片中叶绿素的积累。根据这些结果对益母草的需肥特性进行了讨论。     

明胶/海藻酸钠/沙蒿胶复合水凝胶的制备及表征

为探究明胶（G）、海藻酸钠（SA）,沙蒿胶（ASKG）对复合水凝胶的力学性能、溶胀和保湿性能的影响,采用共混-离子交联法制备海藻酸钠/明胶/沙蒿胶复合水凝胶,并对制得的水凝胶进行结构表征和溶血率测试。结果表明:当G质量分数为2.5%,SA为1.5%,ASKG为0.7%时,复合水凝胶压缩强度达到427.2 kPa,拉伸强度达到563.449 kPa,断裂伸长率为117%,溶胀率为744%,且具有较好的保湿性能。红外光谱表明,由于沙蒿胶中存在大量羟基,因此加入沙蒿胶后在3 300 cm^-1～3 600 cm^-1羟基峰形变宽。G/SA/ASKG复合水凝胶溶血率低于5%,具有较好的网络孔结构和血液相容性,为复合水凝胶在医用敷料方面的应用提供一定的参考价值。     

Micropropagation of Eucalyptus nitens maiden (Shining gum)

Summary Eucalyptus nitens Maiden (shining gum) is a frost-tolerant species of Eucalyptus that can be used as an alternative species to Eucalyptus globulus in some regions of Portugal where winter temperatures are too low. Seedlings and 1-yr-old shoot tips and nodes were used for micropropagation of E. nitens. The best multiplication rate (2.25) was obtained when seedling shoots (<15 mm) were cultured on a medium containing the major nutrients (at half-strength) and minor elements of Murashige and Skoog (1962) medium, the organics of De Fossard medium (De Fossard et al., 1974) and a combination of benzyladenine (0.9 μM) and 1-naphthaleneacetic acid (0.05 μM). Seedling cuttings (4-,8-, and 10-wk-old) rooted well on media containing several concentrations of 3-indolebutyric acid (4.9, 9.8, and 14.8 μM) or 3-indoleacetic acid (5.7, 11.4, and 17.1 μM), giving frequencies of root induction above 80%. With this type of explant, root formation was also found on basal medium without growth regulators. Rooting of in vitro-propagated shoots obtained from seedlings (8-wk-old) after four subcultures (every 3 wk) was more difficult, with the best results obtained on a medium containing 14.7 μM 3-indolebutyric acid (60.0% root induction). No root formation was achieved when shoots from 1-yr-old explants were used. After a period of 4 mo., 96.3% of the plants transferred to the greenhouse survived acclimatization.     

Ecological niche breadth and microhabitat guild structure in temperate Australian reptiles: Implications for natural resource management in endangered grassy woodland ecosystems

Ecological theory predicts that species with narrow niche requirements (habitat specialists) are more vulnerable to anthropocentric disturbances than those with broad niche requirements (habitat generalists). Hence, understanding a species ecological niche and guild membership would serve as a valuable management tool for providing a priori assessments of a species extinction risk. It also would help to forecast a species capacity to respond to land use change, as what might be expected to occur under financial incentive schemes to improve threatened ecological vegetation communities. However, basic natural history information is lacking for many terrestrial species, particularly reptiles in temperate regions of the world. To overcome this limitation, we collated 3527 reptile observations from 52 species across an endangered woodland ecoregion in south‐eastern Australia and examined ecological niche breadth and microhabitat guild structure. We found 30% of species had low ecological niche values and were classified as habitat specialists associated with large eucalypt trees, woody debris, surface rock or rocky outcrops. Cluster analysis separated species into six broad guilds based on microhabitat similarity. Approximately 80% of species belonged to guilds associated with old growth vegetation attributes or non‐renewable litho‐resources such as surface rock or rocky outcrops. Our results suggest that agri‐environment schemes that focus purely on grazing management are unlikely to provide immediate benefits to broad suites of reptiles associated with old growth vegetation and litho‐resources. Our classification scheme will be useful for identifying reptile species that are potentially vulnerable to anthropocentric disturbances and may require alternative strategies for improving habitat suitability and reptile conservation outcomes in grassy woodland ecosystems.     

高粘发酵体系不同搅拌桨的CFD模拟及发酵验证

搅拌桨是高好氧高黏度微生物发酵实现高效反应必不可少的因素之一,不同搅拌桨组合对发酵过程的影响十分重要。威兰胶是由产碱杆菌在高耗氧高粘度发酵体系下合成的胞外微生物多糖,广泛应用于水泥、石油、油墨、食品等行业中。本研究借助于计算流体力学(Computational fluid dynamics,CFD)的方法,以威兰胶发酵液体系为研究体系,研究了6种不同搅拌桨组合在反应器内流体速率分布、剪切速率、和气含率等参数。将模拟效果较好的3种组合用于威兰胶发酵过程。研究表明MB-4-6搅拌桨组合对改善发酵罐内部的溶氧及流场分布效果最明显,威兰胶产量水平提高了13%。同时在该组合下威兰胶的产品粘度得到有效提高。     

Guar gum: a cheap substitute for agar in microbial culture media

AIMS: To determine the possibility of using guar gum, a colloidal polysaccharide, as a cheap alternative to agar for gelling microbial culture media. METHODS AND RESULTS: As illustrative examples, 12 fungi and 11 bacteria were cultured on media solidified with either guar gum or agar. All fungi and bacteria exhibited normal growth and differentiation on the media gelled with guar gum. Microscopic examination of the fungi and bacteria grown on agar or guar gum gelled media did not reveal any structural differences. However, growth of most of the fungi was better on guar gum media than agar, and correspondingly, sporulation was also more advanced on the former. Bacterial enumeration studies carried out for Serratia sp. and Pseudomonas sp. by serial dilution and pour-plate method yielded similar counts on both agar and guar gum. Likewise, a selective medium, succinate medium used for growth of Pseudomonas sp. did not support growth of Bacillus sp. when inoculated along with Pseudomonas on both agar or guar gum supplemented medium. CONCLUSIONS: Guar gum, a galactomannan, which is 50 times cheaper than Difco-bacto agar, can be used as a gelling agent in place of agar in microbial culture media. SIGNIFICANCE AND IMPACT OF THE STUDY: As the media gelled with guar gum do not melt at temperature as high as 70 degrees C, these can be used for isolation and maintenance of thermophiles.