嗜热菌对有机污染物的降解及其应用研究进展

有机污染物造成的环境问题日趋严重,嗜热菌具有高效降解环境有机污染物的潜力.嗜热菌在高温条件下降解有机污染物,代谢速度快,嗜温杂菌的竞争减少,同时高温环境下一些难降解有机物的溶解度和生物可利用性大大提高,有机污染物可得到快速、彻底降解.因此,嗜热菌对有机废水生物处理及有机物污染场地生物修复等意义重大.本文从嗜热菌降解有机污染物的特点、温度的影响、降解途径、降解酶及其编码基因及工程应用等角度,介绍了嗜热菌降解有机污染物的研究进展,并对嗜热菌降解有机污染物的机理、菌种资源储备、技术策略及应用研发等研究方向进行了展望.     

嗜热性木质纤维素酶在纤维素乙醇生产中的研究进展

聚焦于嗜热性木质纤维素酶在纤维素乙醇生产中的应用,归纳了限制纤维素乙醇商业化的技术瓶颈,简单介绍了嗜热性木质纤维素酶的特点,重点介绍了嗜热性木质纤维素酶在筛选、修饰、固定化、异源表达、代谢调控以及协同作用中的研究进展,讨论了嗜热性木质纤维素酶在纤维素乙醇生产中发挥的作用。最后,提出了嗜热性木质纤维素酶在纤维素乙醇生产中面临的问题并展望了其应用前景。     

代谢木糖产乙醇的酿酒酵母工程菌研究进展

随着能源价格的持续上涨,使用木质纤维素生产燃料乙醇已具有重要的实践意义.木糖是多数木质纤维素水解产物中含量仅次于葡萄糖的一种单糖,传统乙醇生产菌株酿酒酵母不能利用木糖,这为使用以木质纤维素为原料发酵生产乙醇带来了困难.多年以来人们试图通过基因工程和细胞融合等方法对其进行改造使其能够代谢木糖生产乙醇.本文主要介绍这方面的研究进展.     

纤维素乙醇高温发酵的研究进展与展望

利用高温细菌发酵,纤维素乙醇生产有望实现“生物质降解-乙醇发酵-乙醇蒸馏”过程的同步化,从而最大限度地降低纤维素乙醇的生产成本;这是一个目标更高、道路更远、科学性更强的可再生能源发展策略.纤维素乙醇高温发酵研究已经取得了重要进展,目前面临的主要挑战包括发酵乙醇的高温细菌的遗传转化系统不够稳定、缺少内源的高活性和耐热性纤维素酶,以及乙醇代谢调控机理有待进一步解析.这些科技难题将会在DNA生物合成和进化技术、细胞生物学技术,以及合成生物学技术的发展中得到解决.     

代谢木糖产乙醇的酿酒酵母工程菌研究进展

随着能源价格的持续上涨, 使用木质纤维素生产燃料乙醇已具有重要的实践意义。木糖是多数木质纤维素水解产物中含量仅次于葡萄糖的一种单糖, 传统乙醇生产菌株酿酒酵母不能利用木糖, 这为使用以木质纤维素为原料发酵生产乙醇带来了困难。多年以来人们试图通过基因工程和细胞融合等方法对其进行改造使其能够代谢木糖生产乙醇。本文主要介绍这方面的研究进展。     

五株木糖利用酵母的生理代谢特性

摘要:【目的】木质纤维素是地球上最丰富的可再生资源,筛选具有高抗逆和高效利用木糖能力的菌株对纤维素类可再生资源综合利用具有重大意义。【方法】论文以5株利用木糖的酵母,即树干毕赤酵母(Scheffersomyces stipitis,S.stipitis)、Candida tenuis (C.tenuis)、Spathaspora passalidarum (S.passalidarum)、Candida amazonensis(C. amazonensis)和Candida jeffriesii(C. jeffriesii)为研究对象,研究了其对温度、乙醇浓度、渗透压的耐受性,采用杜氏小管实验研究了其对常用碳源和氮源的利用能力,另外通过木糖发酵实验初步研究了被测试酵母在有氧和限氧条件下的木糖发酵性能。【结果】结果表明,S. passalidarum能够耐受44 ℃左右的高温,对多种碳源和氮源具有较强的利用能力,此外,S. passalidarum在有氧与限氧条件下均能快速代谢木糖,限氧条件下乙醇得率达0.43 g/g。C. amazonensis对纤维二糖具有较强发酵能力,代谢木糖产生木糖醇和少量乙醇,同时该酵母耐受温度在42 ℃左右。综合比较,其他酵母在实验过程中没有表现出明显优势。【结论】S. passalidarum 在纤维素工业化应用中是一株良好的生产候选菌株。此外,C. amazonensis具有较强的木糖醇生产能力,有望成为一株优良的木糖醇生产菌株。     

木质纤维素稀酸水解糖液乙醇发酵研究进展

以木质纤维素为原料生产燃料乙醇,首先要对原料进行预处理得到可发酵糖,在稀酸水解木质纤维素得到的糖液中,除含有葡萄糖、木糖等六碳糖和五碳糖外,根据水解温度、酸浓度和时间的不同,还含有不同浓度的发酵抑制剂。因此,在研究木质纤维素稀酸水解糖液的乙醇发酵中,对代谢木糖成乙醇的菌种的研究、对耐/代谢发酵抑制剂微生物的研究、对稀酸水解糖液的脱毒方法的研究以及对稀酸水解糖液不同发酵方式的乙醇发酵研究等非常重要。重点介绍了以上几个方面近几年研究的进展。     

小分子封闭提高固定化嗜热菌蛋白酶的热稳定性

为了提高固定化嗜热菌蛋白酶的热稳定性,在制备共价固定化嗜热菌蛋白酶的基础上,通过选择氨基酸和醇类小分子来封闭载体表面未反应的活化基团,并考察了固定化酶的催化活性及热稳定性。结果发现：L-Trp和L-Val封闭修饰固定化酶时,在80℃的水浴中加热150 min后其剩余活力仍为93.4%和98.6%,其效果约为未经小分子封闭的固定化嗜热菌蛋白酶的2倍。所筛选的几种小分子物质中,叔戊醇、L-Trp、L-Val及L-Ala不仅能提高固定化嗜热菌蛋白酶的热稳定性,而且也可以提高固定化酶的相对活力,从而更有利于其在工业生产中的应用。     

麦芽糖假丝酵母菌混合糖代谢的发酵特性

葡萄糖和木糖的混合糖共代谢是木质纤维素资源高效转化利用的关键环节。利用本实验室保藏的天然木糖利用酵母菌,麦芽糖假丝酵母(Candida maltosa)Xu316,本研究对该菌代谢利用不同比例的葡萄糖、木糖发酵特性进行了系统测试,总结了麦芽糖假丝酵母混合糖代谢的一般规律。研究结果表明麦芽糖假丝酵母菌具有较高的葡萄糖利用率和木糖醇积累能力。在糖浓度低于20%时,该菌可以共同利用葡萄糖和木糖,最大乙醇产量和木糖醇产量分别为0.43g·g-1和0.58g·g-1,具有工业应用生产生物基产品的潜力。     

运动发酵单胞菌在生物炼制中的研究进展

以木质纤维素生物质为原料的生物炼制技术已成为全球研发的热点和难点。欧盟国家和美国的中长期生物质能源发展路线图中均将木质纤维素生物炼制技术作为重要目标,但是目前整体水平尚处于中试阶段。我国的纤维素类生物质原料非常丰富,将其转化成燃料乙醇及生物基础化学品等具有较大的潜力,但当前要想实现商业化生产,还面临着很多瓶颈问题亟待解决。缺乏能够同时高效利用纤维素类水解物的发酵菌株,已成为纤维素生物质高效与高值转化的关键制约因素。运动发酵单胞菌是目前唯一一种通过ED途径兼性厌氧发酵葡萄糖的微生物,其独特的代谢途径使其成为构建产乙醇工程菌的优选宿主之一;同时由于该菌具有较高的糖利用效率等优点,也是其他生物基化学品生产的重要候选平台微生物,如山梨醇、葡萄糖酸、丁二酸和异丁醇等。本文从该菌的研究历程、分子生物学基础、菌种改良及该菌在生物能源及生物基化学品等生物炼制体系中的应用研究角度进行了综述,并提出该菌可作为纤维素生物质生物炼制系统的新的重要平台微生物。     

Role for dopamine in malonate-induced damage in vivo in striatum and in vitro in mesencephalic cultures

Defects in mitochondrial energy metabolism have been implicated in the pathology of several neurodegenerative disorders. In addition, the reactive metabolites generated from the metabolism and oxidation of the neurotransmitter dopamine (DA) are thought to contribute to the damage to neurons of the basal ganglia. We have previously demonstrated that infusions of the metabolic inhibitor malonate into the striata of mice or rats produce degeneration of DA nerve terminals. In the present studies, we demonstrate that an intrastriatal infusion of malonate induces a substantial increase in DA efflux in awake, behaving mice as measured by in vivo microdialysis. Furthermore, pretreatment of mice with tetrabenazine (TBZ) or the TBZ analogue Ro 4-1284 (Ro-4), compounds that reversibly inhibit the vesicular storage of DA, attenuates the malonate-induced DA efflux as well as the damage to DA nerve terminals. Consistent with these findings, the damage to both DA and GABA neurons in mesencephalic cultures by malonate exposure was attenuated by pretreatment with TBZ or Ro-4. Treatment with these compounds did not affect the formation of free radicals or the inhibition of oxidative phosphorylation resulting from malonate exposure alone. Our data suggest that DA plays an important role in the neurotoxicity produced by malonate. These findings provide direct evidence that inhibition of succinate dehydrogenase causes an increase in extracellular DA levels and indicate that bioenergetic defects may contribute to the pathogenesis of chronic neurodegenerative diseases through a mechanism involving DA.     

Changes in lactate dehydrogenase activity in chicken tissues in hyperthyreosis in ontogenesis

The lactate dehydrogenase activity in reactions of lactate oxidation and synthesis was studied in subfractions of the chicken brain, heart and liver at the embryonal, early postembryonal and adult stages of development after thyroxine administration. It has been shown that during embryogenesis thyroxine predominantly enhanced the rate of lactate oxidation in the mitochondrial tissues. A marked increase in the lactate synthesis was found in cytoplasm of the adult chicken tissues. Specificity of enzyme activity alterations was detected in the chicken brain during ontogenesis after thyroxine administration.     

Scurvy in capybaras bred in captivity in Argentine

In order to determine if the absence of vitamin C in the diet of capybaras (Hydrochoerus hydrochaeris) causes scurvy, a group of seven young individuals were fed food pellets without ascorbic acid, while another group of eight individuals received the same food with 1 g of ascorbic acid per animal per day. Animals in the first group developed signs of scurvy-like gingivitis, breaking of the incisors and death of one animal. Clinical signs appeared between 25 and 104 days from the beginning of the trial in all individuals. Growth rates of individuals deprived of vitamin C was considerably less than those observed in the control group. Deficiency of ascorbic acid had a severe effect on reproduction of another population of captive capybaras. We found that the decrease in ascorbic acid content in the diet affected pregnancy, especially during the first stages. The results obtained suggest that it is necessary to supply a suitable quantity of vitamin C in the diet of this species in captivity.     

SSTR5 ablation in islet results in alterations in glucose homeostasis in mice

Somatostatin (SST) peptide is a potent inhibitor of insulin secretion and its effect is mediated via somatostatin receptor 5 (SSTR5) in the endocrine pancreas. To investigate the consequences of gene ablation of SSTR5 in the mouse pancreas, we have generated a mouse model in which the SSTR5 gene was specifically knocked down in the pancreatic beta cells (betaSSTR5Kd) using the Cre-lox system. Immunohistochemistry analysis showed that SSTR5 gene expression was absent in beta cells at three months of age. At the time of gene ablation, betaSSTR5Kd mice demonstrated glucose intolerance with lack of insulin response and significantly reduced serum insulin levels. Insulin tolerance test demonstrated a significant increase of insulin clearance in vivo at the same age. In vitro studies demonstrated an absence of response to SST-28 stimulation in the betaSSTR5Kd mouse islet, which was associated with a significantly reduced SST expression level in betaSSTR5Kd mice pancreata. In addition, betaSSTR5Kd mice had significantly reduced serum glucose levels and increased serum insulin levels at 12 months of age. Glucose tolerance test at an older age also indicated a persistently higher insulin level in betaSSTR5Kd mice. Further studies of betaSSTR5Kd mice had revealed elevated serum C-peptide levels at both 3 and 12 months of age, suggesting that these mice are capable of producing and releasing insulin to the periphery. These results support the hypothesis that SSTR5 plays a pivotal role in the regulation of insulin secretion in the mouse pancreas.