云芝液体培养及富集硒研究

通过云芝 (Polystictusversicolor)液体培养及富集硒研究。在培养温度 2 5～ 2 8℃ ,pH5 5～ 6 0 ,振荡速度 16 0r/min ,培养基中硒含量为 2 0mg/kg的条件下 ,云芝生物转化量及硒回收率最高。

Comparison of Fe^(2+) oxidation by Acidithiobacillus ferrooxidans in rotating-drum and stirred-tank reactors

Fe2＋ oxidation by Acidithiobacillus ferrooxidans（At.ferrooxidans） under different solid contents by adding inert Al2O3 powder was examined in rotating-drum and stirred-tank reactors.The results show that the bioactivity of At.ferrooxidans in the stirred-tank is higher than that in the rotating-drum in the absence of Al2O3 powder,but the biooxidation rate of Fe2＋ decreases markedly from 0.23 g/（L·h） to 0.025 g/（L·h） with increasing the content of Al2O3 powder from 0 to 50%（mass fraction） in the stirred-tank probably due to the deactivation of At.ferrooxidans resulting from the collision and friction of solid particles.The increase in Al2O3 content has a little adverse effect on the bioactivity of At.ferrooxidans in the rotating-drum due to different mixing mechanisms of the two reactors.The biooxidation rate of Fe2＋ in the rotating-drum is higher than that in the stirred-tank at the same content of Al2O3 powder,especially at high solid content.The higher bioactivity of At.ferrooxidans can be maintained for allowing high solid content in the rotating-drum reactor,but its application potential still needs to be verified further by the sulfide bioleaching for the property differences of Al2O3 powder and sulfide minerals.

A field study on the conversion ratio of phytoplankton biomass carbon to chlorophyll-a in Jiaozhou Bay,China

A one-year field study was conducted to determine the conversion ratio of phytoplankton biomass carbon （Phyto-C） to chlorophyll-a （Chl-a） in Jiaozhou Bay, China. We measured suspended particulate organic carbon （POC） and phytoplankton Chl-a samples collected in surface water monthly from March 2005 to February 2006. The temporal and spatial variations of Chl-a and POC concentrations were observed in the bay. Based on the field measurements, a linear regression model Ⅱwas used to generate the conversion ratio of Phyto-C to Chl-a. In most cases, a good linear correlation was found between the observed POC and Chl-a concentrations, and the calculated conversion ratios ranged from 26 to 250 with a mean value of 56 μg ·μl^-1. The conversion ratio in the fall was higher than that in the winter and spring months, and had the lowest values in the summer. The ratios also exhibited spatial variations, generally with low values in the near shore regions and relatively high values in offshore waters. Our study suggests that temperature was likely to be the main factor influencing the observed seasonal variations of conversion ratios while nutrient supply and light penetration played important roles in controlling the spatial variations.

Influence of Conditions on Reuterin Accumulation by the Resting Cell Biotransformation Process

3-Hydroxypropionaldehyde （3-HPA） is a potential valuable chemical and new broad-spectrum antim-icrobial substance. In order to improve the conversion of 3-HPA/glycerol, our work studied the two-step process from glycerol to 3-HPA, and investigated the influence of cell harvest time, glycerol concentration, biomass con-centration, pH and temperature on the production of 3-HPA by Lactobacillus reuteri CG001, respectively. The re-sults showed that molar conversion yield of 3-HPA/glycerol reached 97.9% under the condition that 200 mmol·L-1 glycerol was converted by 25.3 g·L-1 resting cell for 1 h at 30 ℃. The cells could not be reused directly because the L. reuteri almost lost its bioconversion activity completely, but the ability of glycerol conversion could gradually recover if the fresh medium was added to the deactivated cell for 4 h.

Determination of Selected Toxic Elements in Apples from Organic Farming

Due to the elevated ecological awareness nowadays the consumption of products of organic agriculture is increasing. Organic farming means excluding the use of synthetic inputs, such as synthetic fertilizers and pesticides or genetically modified organisms, but there are only a few regulations regarding heavy metal concentrations in soils. Thus a not negligible uptake of metals from the soil where the apple trees are grown may occur. Furthermore inorganic copper compounds being traditional fertilizers for apple trees are not considered as synthetic fertilizers, thus they are still used in organic apple farming for soil or foliar application. Thus also apples produced by organic agriculture may contain toxic elements, such as cadmium, chromium, copper, and lead. The concentrations of these elements were determined in whole apples, as well as in the flesh and peel in order to estimate the possible risk for human health. Prior to analysis using ICP-AES samples underwent a microwave assisted digestion. The LODs obtained are below the recommended maximum levels in vegetables/fruits by WHO. In all samples no Cu, Cr, and Pb could be detected. Only Ca was found in the peel of about a third of samples investigated in concentrations between LOD and LOQ （1-3 μg/g）.

Soil Enzyme Activities on Eroded Slopes in the Sichuan Basin, China

Determining how soil erosion affects enzyme activity may enhance our understanding of soil degradation on eroded agricultural landscapes. This study assessed the changes in enzyme activity with slope position and erosion type by selecting water and tillage erosion-dominated slopes and performing analyses using the 1376s technique. The 137Cs data revealed that soil loss occurred in the upper section of the two eroded slope types, while soil accumulation occurred in the lower section. The invertase activity increased downslope and exhibited a pattern similar to the 137Cs data. The spatial patterns of urease and alkaline phosphatase activities were similar to the 137Cs inventories on the water and tillage erosion-dominated slopes, respectively. On both the eroded slope types, the invertase activity and soil organic carbon content were correlated, but no correlation was observed between the alkaline phosphatase activity and total phosphorus content. Nevertheless, the urease activity was correlated with the total nitrogen content only on the water erosion-dominated slopes. The enzyme activity-to-microbial biomass carbon ratios indicated high activities of invertase and urease but low activity of phosphatase on the water erosion-dominated slopes compared with the tillage erosion-dominated slopes. Both the invertase activity and the invertase activity-to-microbial biomass carbon ratio varied with the slope position. Changes in the urease activity-to-microbial biomass carbon ratio were significantly affected by the erosion type. These suggested that the dynamics of the invertase activity were linked to soil redistribution on the two eroded slope types, whereas the dynamics of the urease and alkaline phosphatase activities were associated with soil redistribution only on the water or tillage erosion-dominated slopes, respectively. The erosion type had an obvious effect on the activities of invertase, urease and alkaline phosphatase. Soil redistribution might influence the involvement of urease in the N cycle and alkaline phosphatase in the P cycle. Thus, enzyme activity-to-microbial biomass ratios may be used to better evaluate microbiological activity in eroded soils.

Intrinsic advantages of Cheilomenes sexmaculata over two coexisting Coccinella species （Coleoptera：Coccinellidae）

Development, survival and reproductive performance of coexisting ladybird species, viz. Cheilomenes sexmaculata, Coccinella septempunctata, and Coccinella transversalis, of the tribe Coccinellini were studied and compared to assess their coexistence and ecological relationships. High values of life history parameters, viz. developmental rate,immature survival, fecundity, egg viability, reproductive rate and conversion of efficiency of ingested food were recorded for C. sexmaculata followed by C. transversalis and C.septempunctata suggesting that the former has intrinsic advantages over the latter two species. This could possibly counterbalance its disadvantages, like relatively smaller size and weight, thereby making it competitive. The developmental period increased with increase in body size. Exceptionally high fecundity after single mating has been recorded in C. sexmaculata. The egg viability, however, was lower than in both Coccinella species.