Growth and pigment composition in the red alga <Emphasis Type="Italic">Halymenia floresii</Emphasis> cultured under different light qualities

Halymenia floresii is an edible species consumed in some Asian markets. In the Yucatan peninsula coast of Mexico, H. floresii dominates rocky substrata between 3 and 40 m where it grows up to 50 cm high. After analyzing the seasonal pattern of pigment content on H. floresii, we evaluate if and how the spectral composition of light affects growth and pigment dynamics under laboratory cultivation. Unialgal cultures were exposed to white, blue, red and green light in a 3-week experiment. Green light resulted in the highest algal growth rates. Synthesis of chlorophyll a, α-carotene and lutein, but not of β-carotene, was induced by white or green light. Phycocyanin synthesis was stimulated by blue light and phycoerythrin synthesis by blue or red light. Light quality treatments may be used to manipulate pigment composition in Halymenia floresii cultures.     

Growth dynamics of Dracaena cinnabari under controlled conditions as the most effective way to protect endangered species

Dracaena cinnabari Balf. fil. is an endangered endemic species growing on the Yemeni island of Soqotra. Dracaena woodlands are considered as one of the oldest forest communities on Earth. Uncontrolled grazing unfortunately caused a lack of naturally occurring regeneration. Our two-year research was focused on the growth dynamics of Dracaena seedlings from two separate populations. One hundred of germinated seeds from two different altitudes from the island were sown and planted under the same conditions. Average increment and difference between the growth dynamics of plants from the two localities were investigated. The observed data on this plant species revealed very interesting, hitherto unknown results. (1) The seedlings germinated within a time period from four to ten weeks. Germination rate was 90% on the Firmihin highland plateau and 78% on the Scand Mountain. (2) Average plant length from both localities was almost the same (24.9 cm) at the end of measurement. Differences in values between the two populations proved as non-significant. (3) A significant difference was found in the number of leaves and in the sum of lengths of all leaves on one plant. While the seedlings from Firmihin featured a wide spreading above-ground part with a large number of leaves, the plants from Scand invested more energy into faster leaves elongation rate. (4) Growth dynamics reflected seasonal changes. Increments were slower or ceased during the period of vegetative rest from autumn to spring. (5) Average mortality rate was 13%. Most of the plants died during the period of vegetative rest. Further study on germination and regeneration under artificial conditions seems like the only way to prevent species extinction.     

枣园桃蛀果蛾寄生蜂种类及其与寄主的关系

桃蛀果蛾(Carposina sasakii Matsumura)是我国十分重要的果实性害虫,其中枣受害最严重,因其幼虫在果实内蛀食危害、高度隐蔽性的生活而较难防治。寻找有效天敌,开展生物防治成为必然。2009年与2010年研究调查了我国大枣部分产区陕西、山西、河南与宁夏枣园桃蛀果蛾寄生性天敌,共发现了3种寄生蜂,即中华齿腿姬蜂(Pristomerus chinensis Ashmead)、章氏小甲腹茧蜂(Chelonus(Microchelonus)zhangi Zhang)和金小蜂(Pteromalidae),3种寄生蜂均从桃蛀果蛾的茧中羽化而出,其中中华齿腿姬蜂和章氏小甲腹茧蜂为优势天敌,但它们表现出十分明显的地域性分布。同时,对中华齿腿姬蜂和章氏小甲腹茧蜂羽化、寄生率以及与寄主之间的关系进行了初步研究,结果表明,中华齿腿姬蜂越冬代成虫出蛰活动始于6月中旬,越冬代寄生率较低,第1代成虫羽化在8月下旬至9月上旬,这代寄生蜂具有较高的寄生率,可达25%;章氏小甲腹茧蜂第1代成虫羽化集中在8月中下旬和9月上旬,由于在2009年与2010年对样地进行不施用杀虫剂的管理,该天敌在2010年自然寄生率显著提高,最高时可达64.52%。因此,科学管理,合理保护与利用当地天敌成为实现该害虫生物防治的关键。     

Putting cells under pressure: a simple and efficient way to enhance the productivity of medium-chain-length polyhydroxyalkanoate in processes with Pseudomonas putida KT2440

The success of bioprocess implementation relies on the ability to achieve high volumetric productivities and requires working with high‐cell‐density cultivations. Elevated atmospheric pressure might constitute a promising tool for enhancing the oxygen transfer rate (OTR), the major growth‐limiting factor for such cultivations. However, elevated pressure and its effects on the cellular environment also represent a potential source of stress for bacteria and may have negative effects on product formation. In order to determine whether elevated pressure can be applied for enhancing productivity in the case of medium‐chain‐length polyhydroxyalkanoate (mcl‐PHA) production by Pseudomonas putida KT2440, the impact of a pressure of 7 bar on the cell physiology was assessed. It was established that cell growth was not inhibited by this pressure if dissolved oxygen tension (DOT) and dissolved carbon dioxide tension (DCT) were kept below ～30 and ～90 mg L^?1, respectively. Remarkably, a little increase of mcl‐PHA volumetric productivity was observed under elevated pressure. Furthermore, the effect of DCT, which can reach substantial levels during high‐cell‐density processes run under elevated pressure, was investigated on cell physiology. A negative effect on product formation could be dismissed since no significant reduction of mcl‐PHA content occurred up to a DCT of ～540 mg L^?1. However, specific growth rate exhibited a significant decrease, indicating that successful high‐cell‐density processes under elevated pressure would be restricted to chemostats with low dilution rates and fed‐batches with a small growth rate imposed during the final part. This study revealed that elevated pressure is an adequate and efficient way to enhance OTR and mcl‐PHA productivity. We estimate that the oxygen provided to the culture broth under elevated pressure would be sufficient to triple mcl‐PHA productivity in our chemostat system from 3.4 (at 1 bar) to 11 g L^?1 h^?1 (at 3.2 bar). Biotechnol. Bioeng. 2012; 109:451–461. © 2011 Wiley Periodicals, Inc.