A truncated antenna mutant of Chlamydomonas reinhardtii can produce more hydrogen than the parental strain

Photoproduction of H(2) gas was examined in the Chlamydomonas reinhardtii tla1 strain, CC-4169, containing a truncated light-harvesting antenna, along with its parental CC-425 strain. Although enhanced photosynthetic performance of truncated antenna algae has been demonstrated previously (Polle etal. Planta 2003; 217:49-59), improved H(2) photoproduction has yet to be reported. Preliminary experiments showed that sulfur-deprived, suspension cultures of the tla1 mutant could not establish anaerobiosis in a photobioreactor, and thus, could not photoproduce H(2) gas under conditions typical for the sulfur-deprived wild-type cells (Kosourov et al. Biotech Bioeng 2002; 78:731-40). However, they did produce H(2) gas when deprived of sulfur and phosphorus after immobilization within thin (similar to 300 mu m) alginate films. These films were monitored for long-term H(2) photoproduction activity under light intensities ranging from 19 to 350 mu E m(-2) s(-1) PAR. Both the tla1 mutant and the CC-425 parental strain produced H(2) gas for over 250 h under all light conditions tested. Relative to the parental strain, the CC-4169 mutant had lower maximum specific rates of H(2) production at low and medium light intensities (19 and 184 mu E m(-2) s(-1)), but it exhibited a 4-times higher maximum specific rate at 285 mu E m(-2) s(-1) and an 8.5-times higher rate at 350 mu E M(-2) s(-1) when immobilized at approximately the same cell density as the parental strain. As a result, the CC-4169 strain accumulated almost 4-times more H(2) than CC-425 at 285 mu E M(-2) s(-1) and over 6-times more at 350 mu E M(-2) s(-1) during 250-h experiments. These results are the first demonstration that truncating light-harvesting antennae in algal cells can increase the efficiency of H(2) photoproduction in mass culture at high light intensity. (C) 2010 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved

Sustained hydrogen photoproduction by phosphorus-deprived Chlamydomonas reinhardtii cultures

This study demonstrates that, besides sulfur deprivation, sustained H-2 photoproduction in Chlamydomonas reinhardtii cultures can be generated by incubating algae under phosphorus-deprived (-P) conditions. However, phosphorus deficiency in algal cells could not be obtained by resuspension of algae in -P medium, evidently due to a significant reserve of phosphorus in cells. In this study, phosphorus deficiency was accomplished by inoculating the washed algae into the -P medium at low initial cell densities (below 2 mg Chl l(-1)). After the initial growth period, where cells utilize intracellular phosphorus, algae established anaerobic environment followed by the period of H-2 photoproduction. The maximum H-2 output (similar to 70 ml l(-1)) was obtained in cultures with the initial Chl content similar to 1 mg l(-1). Cultures with Chl above 2 mg l(-1) did not produce H-2 gas. The physiological response of algal cultures to phosphorus deprivation demonstrated significant similarities with the response of algae to sulfur depletion. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved

The Will of Eustathios Boilas in the Context of Byzantine-Georgian Political Relations in the 11th Century

ntroduction. The article considers the data of the Will of the Byzantine nobleman Eustathios Boilas about his possessions in the Byzantine theme Iberia and Great Armenia in the context of political relations between Byzantium and the Georgian Kingdom in the 1040s and 1050s. Methods. The comparison of the texts of different written traditions is carried out. The data of the Will of Eustathios Boilas is analyzed in the context of “Chronicle of Kartli” from the corpus of the Kartlis Tskhovreba and the other sources. Analysis. The comparison of information from all the texts indicates that Boilas’ possessions even reached beyond the theme of Iberia, in particular, to the Northern Tao and part of Klarjeti. From the late 30s of the 11th century this territory became the arena of a cruel Georgian civil conflict between the Georgian king Bagrat IV and the Byzantium ally, the Duke of Kldekari Liparit IV Baghuashi. The defeat of Liparit in this conflict between 1053 and 1057 forced Byzantium to abandon its new acquisitions in Northern Tao, as a result of which, among other things, Eustathios Boilas lost several of his lands, which were transferred to Bagrat IV and his allies. Results. As the study shows, the borders of the theme Iberia and Great Armenia in the period from 1047 to 1053/1057 expanded to the north, including the territory of the Northern Tao and possibly part of Klarjeti, which was ruled by the Byzantine ally Liparit. The combination of data from both Byzantine and Georgian texts assumes to revise the generally accepted point of view about the administrative boundaries of the Iberia and Great Armenia theme

Hydrogen photoproduction under continuous illumination by sulfur-deprived, synchronous Chlamydomonas reinhardtii cultures

Unsynchronized Chlamydomonas reinhardtii cells subsequently deprived of sulfur produce H-2 under continuous illumination in the laboratory for 3-4 days. However, cultures grown outdoors will be exposed to day-and-night cycles that may synchronize their growth and cell division. While it is clear that only insignificant amounts of H-2 can be produced by sulfur-deprived cells during the night period, little work has been done to examine the effects of the light/dark cycles preceding sulfur deprivation on subsequent H-2 photoproduction. We show that (a) C reinhardtii cells exhibit synchronized growth and cell division in the presence of acetate, (b) cells with the highest specific rates of H-2 photoproduction also have the highest rates of biomass accumulation, and (c) the highest rates of starch and protein degradation coincide with the highest rates of formate and acetate accumulation, but not with H-2 photoproduction. This work shows that it is possible to maximize the production of H-2 by sulfur-depriving synchronized cultures at about 4 h after the beginning of the light period. <br /

Continuous hydrogen photoproduction by Chlamydomonas reinhardtii

This study demonstrates, for the first time, that it is possible to couple sulfate-limited Chlamydomonas reinhardtii growth to continuous H-2 photoproduction for more than 4000 h. A two-stage chemostat system physically separates photosynthetic growth from H-2 production, and it incorporates two automated photobioreactors (PhBRs). In the first PhBR, the algal cultures are grown aerobically in chemostat mode under limited sulfate to obtain photosynthetically competent cells. Active cells are then continuously delivered to the second PhBR, where H2 production occurs under anaerobic conditions. The dependence of the H-2 production rate on sulfate concentration in the medium, dilution rates in the PhBRs, and incident light intensity is reported

К вопросу о датировке получения титула куропалата правителем Тао-Кларджети Давидом III

The article is devoted to a new examination of the issue of the date of obtaining the title of kouropalates by the ruler of Tao-Klarjeti David III (966–1000) from the Byzantine authorities. Manuscripts’ analysis and source criticism of Iviron’s acts, “History of the Bagratids” by Sumbat Davitis-Dze and “Annals” by Yahya of Antioch together with the already known data of other narrative sources and epigraphy make it possible to offer 983 as a new date for obtaining the title by David III. In addition, for the first time in the historiography, author offer an explanation about so long rejection of Byzantium to award the ruler of the South Tao by the title of kouropalates. The author comes to the conclusion that this position of the empire was the result of David’s participation around 961 in the organization of the exile and death of his own father, kuropalates Adarnase, who was an ally of Constantinople and a legitimate ruler in the Tao region from the empire’s point of view. The David III’s desire to get the title is explained by the his will to obtain an additional factor for his own legitimation in the Tao region, without the alacrity to join the Byzantine “hierarchy of power”. The proof of this is all foreign policy of ruler of Tao in relations with Byzantium before 990.Статья посвящена новому рассмотрению вопроса о дате получения титула куропалата правителем Южного Тао Давидом III Великим (966-1000) от византийских властей. Источниковедческий анализ рукописей актов Иверского монастыря на Афоне, в частности, рукописи известного картвельского военачальника и церковного деятеля Торникия, а также текстов «Истории и повествования о Багратионах» Сумбата Давитисдзе из грузинского летописного свода «Картлис Цховреба» и арабоязычной «Летописи» византийского писателя Яхьи Антиохийского вместе с уже известными данными других нарративных источников и эпиграфики позволяют предложить 983 г. в качестве новой датировки получения титула Давидом III. Помимо этого, впервые в исторической науке сделана попытка объяснить причину столь долгого отказа Византии от присуждения куропалатства данному представителю тао-кларджетских Багратидов. Автор приходит к выводу, что такая позиция империи являлась следствием прямого участия Давида III в организации пострижения в монахи и смерти собственного отца куропалата Адарнасе около 961 г., который являлся союзником Константинополя, отличившимся в сражениях с арабами, и легитимным с точки зрения империи правителем в Таойском регионе. Стремление самого Давида III к обладанию титулом куропалата объясняется желанием получить дополнительный фактор для легитимации, полученной с помощью узурпации собственной власти в Южном Тао, без готовности встроиться в т. наз. византийскую «иерархию власти». Доказательством этого является вся внешнеполитическая деятельность таойского властителя в отношениях с Византией до 990 г., напрямую касавшаяся и «внутрикартвельской» политики в Абхазском царстве и Картли

Два посольства Баграта IV в Константинополь: датировка, причины и последствия

This article is devoted to a new consideration of the issue of the number and dating of the embassies of king Bagrat IV of Georgia (1027–1072) to Constantinople during the reign of the Byzantine emperor Constantine IX Monomachos (1042–1055). Contrary to I. A. Javakhishvili’s point of view, generally accepted in historiography about the existence of the only embassy of Bagrat IV to Byzantium in 1054–1057, the author promotes the hypothesis about the existence of two embassies, in 1047 and 1050–1052/1053 respectively. This hypothesis is proved, in addition to the source analysis of the Georgian text of the Chronicle of Kartli, by referring to Byzantine and Armenian narrative sources, as well as by using information from the recently explored manuscript Q-1376 from the Georgian National Centre of Manuscripts. A comparison of data from sources allows the author to link the reason for the two embassies of the Georgian king to Byzantium with the escalation of the internal Georgian conflict between Bagrat IV and Liparit IV Baghuashi, Duke of Kldekari after the Battle of Sasireti in 1046. Also, the article highlights several new features in it, in particular, the conditions of truces between the two sides, the date of Liparit’s liberation from the Seljuk captivity, as well as the possible participation in the conflict of Leonti Mroveli, a famous Georgian historian of the eleventh century. Also, the article examines the consequences of the two trips of Bagrat IV to Constantinople for the Byzantine foreign policy on its eastern borders and, more particularly, clarifies the dating and circumstances of the military campaign of raiktor Nikephoros against the Shaddadid emir of Dvin Abu’l-Aswar in 1049, as well as the role of Georgian noblemen in this campaign.Статья посвящена новому рассмотрению вопроса о количестве и датировке посольств грузинского царя Баграта IV (1027–1072) в Константинополь в период правления византийского императора Константина IX Мономаха (1042–1055). Вопреки общепринятой в историографии точке зрения И. А. Джавахишвили о существовании единственного посольства Баграта IV в Византию в 1054–1057 гг., автор выдвигает гипотезу о существовании двух посольств, в 1047 г. и 1050–1052/1053 гг. соответственно. Эта гипотеза доказывается, помимо источниковедческого анализа грузинского текста «Летописи Картли», с помощью обращения к византийским и армянским нарративным источникам, а также использования сведений недавно исследованной рукописи Q-1376 из Грузинского национального центра рукописей. Сопоставление данных из источников позволяет связать причину двух посольств грузинского царя в Византию с обострением после Сасиретской битвы 1046 г. внутригрузинского конфликта между Багратом IV и клдекарским эриставом Липаритом Багваши и выделить в нем несколько новых особенностей, в частности, условия перемирий между двумя сторонами, дату освобождения Липарита из сельджукского плена, а также возможность участия в этом конфликте знаменитого грузинского историографа XI в. Леонти Мровели. Помимо этого, в статье рассмотрены последствия двух поездок Баграта IV в Константинополь для византийской внешней политики на ее восточных границах и в особенности уточнены датировка и обстоятельства военного похода ректора Никифора против шеддадидского эмира Двина Абу’л-Асвара в 1049 г., а также роль грузинских сановников в этой кампании

A comparison of hydrogen photoproduction by sulfur-deprived Chlamydomonas reinhardtii under different growth conditions

Continuous photoproduction of H-2 by the green alga, Chlamydomonas reinhardtii, is observed after incubating the cultures for about a day in the absence of sulfate and in the presence of acetate. Sulfur deprivation causes the partial and reversible inactivation of photosynthetic O-2 evolution in algae, resulting in the light-induced establishment of anaerobic conditions in sealed photobioreactors, expression of two [FeFe]-hydrogenases in the cells, and H-2 photoproduction for several days. We have previously demonstrated that sulfur-deprived algal cultures can produce H-2 gas in the absence of acetate, when appropriate experimental protocols were used (Tsygankov, A.A., Kosourov, S.N., Tolstygina, IN., Ghirardi, M.L., Seibert, M., 2006. Hydrogen production by sulfur-deprived Chlamydomonas reinhardtii under photoautotrophic conditions. Int. J. Hydrogen Energy 31, 1574-1584). We now report the use of an automated photobioreactor system to compare the effects of photoautotrophic, photoheterotrophic and photomixotrophic growth conditions on the kinetic parameters associated with the adaptation of the algal cells to sulfur deprivation and H-2 photoproduction. This was done under the experimental conditions outlined in the above reference, including controlled pH. From this comparison we show that both acetate and CO2 are required for the most rapid inactivation of photosystem II and the highest yield of H-2 gas production. Although, the presence of acetate in the system is not critical for the process, H-2 photoproduction under photoautotrophic conditions can be increased by optimizing the conditions for high starch accumulation. These results suggest ways of engineering algae to improve H-2 production, which in turn may have a positive impact on the economics of applied systems for H,, production. (c) 2007 Elsevier B.V. All rights reserved

Hydrogen production by sulfur-deprived Chlamydomonas reinhardtii under photoautotrophic conditions

Thus far, all experiments leading to H-2 production by sulfur-deprived cultures of microalga have been done with photoheterotrophic cultures in the presence of acetate, which increases the cost of the H-2 produced. This study demonstrates that sustained H-2 photoproduction by a sulfur-deprived green alga, Chlamydomonas reinhardtii, is possible under strictly photoautotrophic conditions in the absence of acetate or any other organic substrate in the medium. To accomplish this, we used cultures pre-grown with 2% CO2 under low light conditions (25 mu E m(-2) s(-1)) and also supplemented with CO2 during S-deprivation, along with a special light regime. Maximum H-2 production (56.4 +/- 16.7 ml l(-1) culture, equal to 56.4 x 10(-3) m(3) m(-3) culture) was observed with photoautotrophic cultures: (a) supplied with carbon dioxide for the first 24 h of sulfur deprivation, (b) exposed during the O-2-producing stage to high light (110 - 120 mu E m(-2) s(-1)), and (c) then exposed to low light (20 - 25 mu E m(-2) s(-1)) during the O-2-consumption and H-2-production stages. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved

Prolongation of H2 photoproduction by immobilized, sulfur-limited Chlamydomonas reinhardtii cultures

Two approaches to prolong the duration of hydrogen production by immobilized, sulfur-limited Chlamydomonas reinhardtii cells are examined. The results demonstrate that continuous H(2) photoproduction can occur for at least 90 days under constant flow of TAP medium containing micromolar sulfate concentrations. Furthermore, it is also possible to prolong the duration of H(2) production by cycling immobilized cells between minus and plus sulfate conditions. (C) 2008 Elsevier B.V. All rights reserved