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101.
The ability of fungi to degrade lignocellulosic materials is due to their highly efficient enzymatic system. Fungi have two types of extracellular enzymatic systems; the hydrolytic system, which produces hydrolases that are responsible for polysaccharide degradation and a unique oxidative and extracellular ligninolytic system, which degrades lignin and opens phenyl rings. Lignocellulosic residues from wood, grass, agricultural, forestry wastes and municipal solid wastes are particularly abundant in nature and have a potential for bioconversion. Accumulation of lignocellulosic materials in large quantities in places where agricultural residues present a disposal problem results not only in deterioration of the environment but also in loss of potentially valuable material that can be used in paper manufacture, biomass fuel production, composting, human and animal feed among others. Several novel markets for lignocellulosic residues have been identified recently. The use of fungi in low cost bioremediation projects might be attractive given their lignocellulose hydrolysis enzyme machinery. 相似文献
102.
Hernández-Montiel HL Meléndez-Herrera E Cepeda-Nieto AC Mejía-Viggiano C Larriva-Sahd J Guthrie S Varela-Echavarría A 《Developmental biology》2003,255(1):99-112
We have addressed the control of longitudinal axon pathfinding in the developing hindbrain, including the caudal projections of reticular and raphe neurons. To test potential sources of guidance signals, we assessed axon outgrowth from embryonic rat hindbrain explants cultured in collagen gels at a distance from explants of midbrain-hindbrain boundary (isthmus), caudal hindbrain, or cervical spinal cord. Our results showed that the isthmus inhibited caudally directed axon outgrowth by 80% relative to controls, whereas rostrally directed axon outgrowth was unaffected. Moreover, caudal hindbrain or cervical spinal cord explants did not inhibit caudal axons. Immunohistochemistry for reticular and raphe neuronal markers indicated that the caudal, but not the rostral projections of these neuronal subpopulations were inhibited by isthmic explants. Companion studies in chick embryos showed that, when the hindbrain was surgically separated from the isthmus, caudal reticulospinal axon projections failed to form and that descending pioneer axons of the medial longitudinal fasciculus (MLF) play an important role in the caudal reticulospinal projection. Taken together, these results suggest that diffusible chemorepellent or nonpermissive signals from the isthmus and substrate-anchored signals on the pioneer MLF axons are involved in the caudal direction of reticulospinal projections and might influence other longitudinal axon projections in the brainstem. 相似文献
103.
Del Río E Acién FG García-Malea MC Rivas J Molina-Grima E Guerrero MG 《Biotechnology and bioengineering》2005,91(7):808-815
The performance of Haematococcus pluvialis in continuous photoautotrophic culture has been analyzed, especially from the viewpoint of astaxanthin production. To this end, chemostat cultures of Haematococcus pluvialis were carried out at constant light irradiance, 1,220 microE/m2.s, and dilution rate, 0.9/d, but varying the nitrate concentration in the feed medium reaching the reactor, from 1.7 to 20.7 mM. Both growth and biomass composition were affected by the nitrate supply. With saturating nitrate, the biomass productivity was high, 1.2 g/L.d, but astaxanthin accumulation did not take place, the C/N ratio of the biomass being 5.7. Under moderate nitrate limitation, biomass productivity was decreased, as also did biomass concentration at steady state, whereas accumulation of astaxanthin developed and the C/N ratio of the biomass increased markedly. Astaxanthin accumulation took place in cells growing and dividing actively, and its extent was enhanced in response to the limitation in nitrate availability, with a recorded maximum for astaxanthin cellular level of 0.8% of dry biomass and of 5.6 mg/L.d for astaxanthin productivity. The viability of a significant continued generation of astaxanthin-rich H. pluvialis cells becomes thus demonstrated, as also does the continuous culture option as an alternative to current procedures for the production of astaxanthin using this microalga. The intensive variable controlling the behavior of the system has been identified as the specific nitrate input, and a mathematical model developed that links growth rate with both irradiance and specific nitrate input. Moreover, a second model for astaxanthin accumulation, also as a function of irradiance and specific nitrate input, was derived. The latter model takes into account that accumulation of astaxanthin is only partially linked to growth, being besides inhibited by excess nitrate. Simulations performed fit experimental data and emphasize the contention that astaxanthin can be efficiently produced under continuous mode by adjustment of the specific nitrate input, predicting even higher values for astaxanthin productivity. The developed models represent a powerful tool for management of such an astaxanthin-generating continuous process, and could allow the development of improved systems for the production of astaxanthin-rich Haematococcus cells. 相似文献
104.
M. Carmen Martínez-Ballesta Luis López-Pérez Mercedes Hernández Carmen López-Berenguer Nieves Fernández-García Micaela Carvajal 《Phytochemistry Reviews》2008,7(2):251-260
Phytochemicals in vegetables are known to be responsible for protective effects against many human diseases, including cardiovascular
diseases and different types of cancer. Environmental conditions and physiological factors may modify the amounts of these
compounds present in vegetables and fruits, but also crop management strategies could increase the production of phytochemicals.
Therefore, the effects of mineral nutrition, soil composition and water content on the production of phytochemicals have been
considered in the development of different fertilisation strategies, efficient water management and techniques such as grafting.
Finally, the contents of health-promoting compounds in vegetables and fruits depend both quantitatively and qualitatively
on their genetic bases. Thus, conventional breeding and genetic modification have been developed as new methodologies to enhance
the nutritional properties of plants.
M. C. Martínez-Ballesta, L. López-Pérez, M. Hernández, C. López-Berenguer, N. Fernández-García contributed equally. 相似文献
105.
106.
107.
As water and nutrient uptake should be related in the response of plants to salinity, the aim of this paper is to establish whether or not aquaporin functionality is related to H+ -ATPase activity in root cells of pepper ( Capsicum annuum L.) plants. Thus, H+ -ATPase activity was measured in plasma membrane vesicles isolated from roots and aquaporin functionality was measured using a cell pressure probe in intact roots. Salinity was applied as 60 m M NaCl or 60 m M KCl, to determine which ion (Na+ , K+ or Cl− ) is producing the effects. We also investigated whether the effects of both salts were ameliorated by Ca2+ . Similar results were obtained for cell hydraulic conductivity, Lpc , and H+ -ATPase activity, large reductions in the presence at NaCl or KCl and an ameliorative effect of Ca2+ . However, fusicoccin (an activator of H+ -ATPase) did not alter osmotic water permeability of protoplasts isolated from roots. Addition of Hg2+ inhibited both ATPase and aquaporins, but ATPase also contains Hg-binding sites. Therefore, the results indicate that H+ -ATPase and aquaporin activities may not be related in pepper plants. 相似文献
108.
During a survey of mucoralean fungi from a Cerrado reserve (Brazilian savanna) some isolates of a Mucor-like fungus were isolated from soil plates. Characterization based on morphological, physiological and molecular data from translation elongation factor (EF-1α), 28S (D1/D2) and ITS1-5.8S-ITS2 rDNA sequences was made. The isolates produce lateral branches bearing multispored sporangiola in addition to the multispored sporangia and a uniformly septate mycelium as the main differentiating characteristics. To our surprise this fungus possesses two EF-1α genes 1.4 and 1.5 kb long. Evidence from the analyzed datasets supports the delimitation of a new genus and the inclusion of Mucor fuscus based on 28S and ITS rDNA data. 相似文献
109.
In recent years, cell-penetrating peptides have proven to be an efficient intracellular delivery system. The mechanism for CPP internalisation, which first involves interaction with the extracellular matrix, is followed in most cases by endocytosis and finally, depending on the type of endocytosis, an intracellular fate is reached. Delivery of cargo attached to a CPP requires endosomal release, for which different methods have recently been proposed. Positively charged amino acids, hydrophobicity and/or amphipathicity are common to CPPs. Moreover, some CPPs can self-assemble. Herein is discussed the role of self assembly in the cellular uptake of CPPs. Sweet Arrow Peptide (SAP) CPP has been shown to aggregate by CD and TEM (freeze-fixation/freeze-drying), although the internalised species have yet to be identified as either the monomer or an aggregate. 相似文献
110.
Julio Álvarez Andrés Perez Sergio Marqués Javier Bezos Anna Grau Maria Luisa de la Cruz Beatriz Romero Jose Luis Saez Maria del Rosario Esquivel Maria del Carmen Martínez Olga Mínguez Lucía de Juan Lucas Domínguez 《BMC veterinary research》2014,10(1):1-10