Multi-stage development process and model of steam chamber for SAGD production in a heavy oil reservoir with an interlayer.

Steam-assisted gravity drainage (SAGD) is an efficient thermal recovery technique for oil sands and extra heavy oil exploitation. The development of steam chamber goes through multi-stage physical processes for SAGD production in a heavy oil reservoir with an interlayer. In this study, considering the situation that an interlayer is located directly above a pair of horizontal wells, we analyzed the whole process of steam chamber development. We divided the whole process into stages I-V, which are the first rising stage, the first lateral expansion stage, the second rising stage, the second lateral expansion stage and the confinement stage, respectively. Particularly, we further divided stage II into 2 periods and stage IV into 3 periods. These stages and periods can help us understand the development process of steam chamber dominated by an interlayer more profoundly. Based on the divided stages and periods, we established different models of SAGD production by assuming different geometric shapes of steam chamber in different stages and periods. Oval shape was assumed in stages I and III, and inverse triangle shape was hypothesized in stages II, IV and V. The formulas of the front distance of steam chamber and the oil production rate of SAGD were deduced from the established models for different development stages. At the end, we performed two example applications to SAGD production in heavy oil reservoirs with an interlayer. The real oil production rates were matched very well with the theoretical oil production rates calculated by the deduced formulas, which implies the multi-stage development model of steam chamber is of reliability and utility.

[Advances of studies on culture and product functions of Euglena gracilis].

Euglena gracilis is a unicellular eukaryote between animal and plant cells, which is widely distributed in nature. E. gracilis has both plant and animal characteristics, and can grow photoautotrophically, heterotrophically and mixotrophically. E. gracilis also features on abundant and various cellular composition. Recently, extensive researches on unique cellular components of E. gracilis have revealed its application in the field of medicine, food, and feedstuff, in terms of improving immunity, fighting inflammation, and lowering uric acid levels. The application prospects of paramylon in biomedical area were also discovered. As food ingredients, food additives, feedstuffs and cosmetic ingredients, E. gracilis has been certified domestically and overseas. A series of products have been developed overseas, especially in Japan. However, the research and development of E. gracilis are still in its infancy in China, and there is huge space for development. At present, the research and potential application of cultivation and product functions of E. gracilis have been rarely reviewed. This review systematically examines both the domestic and abroad research of cultivation and production of E. gracilis, as well as the biological activity of E. gracilis powder and paramylon. The existing problems in the application, exploitation, and possible development direction of E. gracilis in the future are prospected. This review might be useful for establishing and optimizing large-scale and efficient heterotrophic technology, as well as developing related products of E. gracilis with specific functions.

Artificial neural networks prediction and optimization based on four light regions for light utilization from Synechocystis sp. PCC 6803.

Light is crucial in microalgae growth. However, dividing the microalgae growth region into light and dark regions has limitations. In this study, the light response of Synechocystis sp. PCC 6803 was investigated to define four light regions (FLRs): light compensation region, light limitation region, light saturation region, and photoinhibition region. The proportions of cells' residence time in the FLRs and the number of times cells (NTC) passed through the FLRs in photobioreactors were calculated by using MATLAB. Based on the FLRs and NTC passed through the FLRs, a growth model was established by using artificial neural network (ANN).The ANN model had a validation R2 value of 0.97, which was 76.36% higher than the model based on light-dark regions. The high accuracy of the ANN model was further verified through dynamic adjustment of light intensity experiments.This study confirmed the importance of the FLRs for studying microalgae growth dynamics.

Development of PMA-qPCR assay to accurately and reproducible quantify viable bacteria of Paenibacillus polymyxa.

Paenibacillus polymyxa is an important biocontrol bacterium. The combination of propidium monoazide (PMA) and quantitative polymerase chain reactionq (qPCR) has proven effective in quantifying live bacteria from various microorganisms. The objective was to create a PMA-qPCR assay to precisely and consistently measure the number of living bacteria of biocontrol P. polymyxa. The primers were designed for the spo0A gene of P. polymyxa HY96-2. The optimal conditions for treating the target strain with PMA were a PMA concentration of 15 µg/mL, an incubation time of 5 min, and an exposure time of 10 min. The PMA-qPCR method had a limit of quantification (LOQ) of 1.0 × 103 CFU/mL for measuring the amount of viable P. polymyxa bacteria. The PMA-qPCR method is more sensitive than the qPCR method in detecting viable bacteria in the mixtures of viable and dead bacteria. The accuracy and reproducibility of quantifying viable P. polymyxa bacteria using the PMA-qPCR method were higher compared to the plate count method.

A new PMA-qPCR method for rapid and accurate detection of viable bacteria and spores of marine-derived Bacillus velezensis B-9987.

Marine-derived Bacillus velezensis B-9987 is an important biocontrol bacterium with a broad-spectrum antibacterial effect. The traditional plate counting method is widely used for quantitative detection of viable bacteria and spores but has some disadvantages such as being laborious and time-consuming (at least 24-48 h). This study aimed to develop a new PMA-qPCR method for rapid and accurate detection of viable bacteria and spores of B-9987. The specific primers were designed for qPCR amplification based on the conserved region of the bmmA gene (encoding a malonyl CoA-ACP transacylase) of B-9987. According to the characteristic that propidium monoazide (PMA) dye can distinguish viable and dead bacteria, the optimal PMA concentration of 10 µg/ml and optimal exposure time of 10 min were achieved under PMA treatment conditions. The B-9987 spores' genomic DNA was successfully extracted after the spore coat was removed and spore germination was induced. The quantification limits of the PMA-qPCR method were determined for viable B-9987 bacteria, spores in pure culture, and spores in marine Bacillus wettable powder (marine Bacillus WP) and were 1.5 × 103 CFU/ml, 6.5 × 102 CFU/ml, and 103 CFU/ml, respectively. Compared with the qPCR method, the PMA-qPCR method could sensitively detect viable bacteria in the viable/dead bacterial mixture. In this study, the developed PMA-qPCR method was found to have excellent sensitivity and specificity in the context of a pure culture of B-9987 strain, which could accurately and rapidly detect viable B-9987 bacteria within 3-4 h and viable B-9987 spores in marine Bacillus WP within 4-6 h.

Controlling average number of photons received per biomass to promote the growth of Synechocystis sp. PPC 6803.

To investigate the actually received light of cells in the photo bioreactor, a light attenuation model of Synechocystis sp. PCC 6803 was established. The relationship between the average number of photons received per biomass (APRPB) and the growth of cell was analyzed. The results demonstrated, Cornet model was accurately fitted with the light attenuation of Synechocystis sp. PCC 6803 and the cell growth rate was affected by APRPB. When the value of APRPB is 3.2 µmol g-1 s-1, the cell have the maximum light efficiency. A maximum specific growth rate of 0.05 h-1 was achieved with APRPB from 3.2 to 12.8 µmol g-1 s-1. After 156 h cultivation, compared to cells cultured under constant light [light intensity: 100 and 1800 µmol/(m2 s)], the DCW under controlled light intensity (light intensity increasing with the cell density) was higher by 79.1% and 20.0%, respectively. This study indicated that APRPB could be used as a light intensity regulation criterion to improve cell production despite different types of reactor and cell density, which provided a theoretical basis for improving the biomass yield of Synechocystis sp. PCC 6803 or other photosynthetic auto-trophic organism.

[Effects of directional adaptation on selenium tolerance and accumulation of heterotrophic Chlorella pyrenoidosa].

Selenium (Se) is an essential trace element for organisms. Se deficiency will cause diseases such as Keshan disease and Kashin-Beck in human being, and huge loss to animal husbandry. Currently available Se supplements have such problems as low Se content, poor bioavailability, and poor safety. Chlorella pyrenoidosa can produce bioavailable and safe organic Se under suitable conditions, which is thus a promising Se supplement. Therefore, in this study, we tried to improve the Se tolerance and accumulation of C. pyrenoidosa by directional adaptation. To be specific, we gradually increased the concentration of Na2SeO3 in medium to domesticate C. pyrenoidosa and optimized the adapting time and concentration gradient of Na2SeO3 during the adaptation. The results showed that the adapted C. pyrenoidosa was more tolerant to Se and had stronger Se enrichment ability. In 5 L fermenter, the adapted strains could tolerate 40 mg/L Na2SeO3 and the synthesis rate of organic Se was 175.6% higher. Then, Se addition method in the 5 L fermenter was optimized. The result demonstrated that addition of Na2SeO3 at 40 mg/L during heterotrophic culture achieved the final dry weight of C. pyrenoidosa cells at 106.4 g/L, content of organic Se at 1 227 mg/kg, and synthesis rate of organic Se at 1.36 mg/(L·h). Compared with the reported highest cell density of 75 g/L and the highest organic Se content of 560 mg/kg, the corresponding figures in this study were 41.9% and 119.1% higher, respectively. In conclusion, directional adaptation can remarkably improve the Se tolerance and enrichment of C. pyrenoidosa.

The optimization of centrifugal pump driving horizontal tubular photobioreactor for enhancing astaxanthin production using heterotrophic Haematococcus pluvialis.

Haematococcus pluvialis is the prime source of natural astaxanthin for commercial exploitation. The large-scale cultivation of H. pluvialis is one of the key technologies for the development of natural astaxanthin industry. So far, horizontal tubular photobioreactor (HTPBR) circulated by a centrifugal pump has been the main PBR for the large-scale cultivation of H. pluvialis. Shear stress is a negative factor in microalgal cultivation at different scales, particularly for large-scale cultivation. To reduce the adverse impact of shear stress, the tolerance of H. pluvialis to the shear stress during the induction stage was first investigated in this study. H. pluvialis aplanospore was not sensitive to stresses between 19.18 and 27.32 Pa, but was resulted in about 30% cell death under shear stress between 27.32 and 63.84 Pa. Accordingly, two centrifugal pumps with different impellers was selected in 400 L HTPBRs to study the outdoor photoinduction for astaxanthin accumulation. The highest astaxanthin productivity and astaxanthin concentration were obtained in HTPBRs using a centrifugal pump equipped with three unshrouded backward-bladed impellers. The HTPBR was then successfully scaled up to 800 L with a similar performance, showing good scalability.

Complete Genome Sequence of Industrial Biocontrol Strain Paenibacillus polymyxa HY96-2 and Further Analysis of Its Biocontrol Mechanism.

Paenibacillus polymyxa (formerly known as Bacillus polymyxa) has been extensively studied for agricultural applications as a plant-growth-promoting rhizobacterium and is also an important biocontrol agent. Our team has developed the P. polymyxa strain HY96-2 from the tomato rhizosphere as the first microbial biopesticide based on P. polymyxa for controlling plant diseases around the world, leading to the commercialization of this microbial biopesticide in China. However, further research is essential for understanding its precise biocontrol mechanisms. In this paper, we report the complete genome sequence of HY96-2 and the results of a comparative genomic analysis between different P. polymyxa strains. The complete genome size of HY96-2 was found to be 5.75 Mb and 5207 coding sequences were predicted. HY96-2 was compared with seven other P. polymyxa strains for which complete genome sequences have been published, using phylogenetic tree, pan-genome, and nucleic acid co-linearity analysis. In addition, the genes and gene clusters involved in biofilm formation, antibiotic synthesis, and systemic resistance inducer production were compared between strain HY96-2 and two other strains, namely, SC2 and E681. The results revealed that all three of the P. polymyxa strains have the ability to control plant diseases via the mechanisms of colonization (biofilm formation), antagonism (antibiotic production), and induced resistance (systemic resistance inducer production). However, the variation of the corresponding genes or gene clusters between the three strains may lead to different antimicrobial spectra and biocontrol efficacies. Two possible pathways of biofilm formation in P. polymyxa were reported for the first time after searching the KEGG database. This study provides a scientific basis for the further optimization of the field applications and quality standards of industrial microbial biopesticides based on HY96-2. It may also serve as a reference for studying the differences in antimicrobial spectra and biocontrol capability between different biocontrol agents.

Dolyemycins A and B, two novel cyclopeptides isolated from Streptomyces griseus subsp. griseus HYS31.

Two novel cyclopeptides with special skeleton, namely, dolyemycins A (1) and B (2) were isolated from Streptomyces griseus subsp. griseus HYS31 by bio-guided isolation. Their structures were elucidated by detailed analysis of spectroscopic data. These two compounds were cyclopeptides containing eleven amino acids including five unusual amino acids (hydroxyglycine, 3-hydroxyleucine, 3-phenylserine, ß-hydroxy-O-methyltyrosine, 2,3-diaminobutyric acid) in both of them and an extra nonprotein amino acids (3-methylaspartic acid) in Dolyemycin B only. Dolyemycins A and B performed antiproliferative activity against human lung cancer A549 cells with IC50 values of 1.0 and 1.2 µM, respectively.

[Bioassay-guided isolation of functional components from hot water extract of Chlorella pyrenoidosa].

The main functional ingredients of hot water extract of Chlorella pyrenoidosa (CPE) were investigated through a bioassay-guided fractionation based on free radical scavenging and macrophage proliferation effects. The main functional ingredients of CPE were polysaccharides (PS) that were isolated by high pressure extraction, Sevag method, ethanol precipitation and ultrafiltration separation. Crude polysaccharides were further separated and purified by ion exchange chromatography DEAE52 and size exclusion chromatography Sephadex G-100. The purified fractions were analyzed by gel permeation chromatography. Molecular weights of the purified fractions PS-1-4-2, PS-1-3-2 and PS-2-3-3 were 3.97×104, 2.28×104 and 4.1×10³ Da, respectively. Bioassay-guided fractionation results indicated that CPE could remove free radicals and promote Ana-1 cells proliferation, mainly due to its various components working together. The components of free radicals scavenging mainly concentrated in PS-1-3, PS-1-4, PS-2-3 and PS-2-4. The components of Ana-1 proliferation mainly concentrated in PS-1-3, PS-1-4 and PS-2-3. This study established the activity screening method of main functional component from CPE, and got three new functional ingredients. It can be used to guide the development of high value products, further promote the industrialization process of microalgae energy, and realize microalgae 'high value products, microalgae energy and microalgae carbon' integration of exemplary role.

Ghanamycins A and B, two novel γ-butyrolactones from marine-derived streptomyces ghanaensis TXC6-16.

Two novel γ-butyrolactones ghanamycins A (1) and B (2) were isolated from the fermentation broth of marine-derived Streptomyces ghanaensis TXC6-16. Their structures were elucidated by spectroscopic analysis. These two novel compounds exhibited antimicrobial activities against some phytopathogens. The minimum IC (MIC) of 2 against Pseudomonas syringae and Erwinia sp. were 50 µg ml-1.

Development of a novel multi-column airlift photobioreactor with easy scalability by means of computational fluid dynamics simulations and experiments.

Aiming to culture algae with high efficiency, a novel vertical multi-column airlift photobioreactor (VMAPBR) has been developed. It was constructed with a series of vertically arranged parallel columns with easy scalability. The hydrodynamic, irradiation and shear stress characteristics of the photobioreactor were studied by computational fluid dynamics (CFD). Accordingly, the optimal aeration manner and aeration rate were determined. When the novel airlift PBR was alternately aerated with aeration rate of 0.2vvm, the biomass concentration of Chlorella pyrenoidosa under outdoor condition reached 1.30gL-1 within the prototype PBR and was further increased to 1.56gL-1 within the optimized PBR. The result of cultivation experiment had good agreement with that of CFD prediction.

A new paradigm for producing astaxanthin from the unicellular green alga Haematococcus pluvialis.

The unicellular green alga Haematococcus pluvialis has been exploited as a cell factory to produce the high-value antioxidant astaxanthin for over two decades, due to its superior ability to synthesize astaxanthin under adverse culture conditions. However, slow vegetative growth under favorable culture conditions and cell deterioration or death under stress conditions (e.g., high light, nitrogen starvation) has limited the astaxanthin production. In this study, a new paradigm that integrated heterotrophic cultivation, acclimation of heterotrophically grown cells to specific light/nutrient regimes, followed by induction of astaxanthin accumulation under photoautotrophic conditions was developed. First, the environmental conditions such as pH, carbon source, nitrogen regime, and light intensity, were optimized to induce astaxanthin accumulation in the dark-grown cells. Although moderate astaxanthin content (e.g., 1% of dry weight) and astaxanthin productivity (2.5 mg L(-1) day(-1) ) were obtained under the optimized conditions, a considerable number of cells died off when subjected to stress for astaxanthin induction. To minimize the susceptibility of dark-grown cells to light stress, the algal cells were acclimated, prior to light induction of astaxanthin biosynthesis, under moderate illumination in the presence of nitrogen. Introduction of this strategy significantly reduced the cell mortality rate under high-light and resulted in increased cellular astaxanthin content and astaxanthin productivity. The productivity of astaxanthin was further improved to 10.5 mg L(-1) day(-1) by implementation of such a strategy in a bubbling column photobioreactor. Biochemical and physiological analyses suggested that rebuilding of photosynthetic apparatus including D1 protein and PsbO, and recovery of PSII activities, are essential for acclimation of dark-grown cells under photo-induction conditions. Biotechnol. Bioeng. 2016;113: 2088-2099. © 2016 The Authors. Biotechnology and Bioengineering Published by Wiley Periodicals, Inc.

A novel paradigm for the high-efficient production of phycocyanin from Galdieria sulphuraria.

A novel cultivation strategy called "Sequential Heterotrophy-Dilution-Photoinduction" was successfully applied in the cultivation of Galdieria sulphuraria for efficient production of phycocyanin (PC). Algae cells were firstly cultivated heterotrophically to achieve high cell density. The maximal dry cell weight of 17.8gL(-1) and maximal biomass productivity of 103.1mgL(-1)h(-1) were obtained. Then, a dilution step was applied to obtain a suitable cell concentration and finally these cells were transferred to high light condition for phycocyanin accumulation. During the photoinduction step, cells could accumulate phycocyanin up to 13.88% of dry cell weight in a cultivation period of 8days. By this technology, total PC productivity far surpassed those reported in all literatures of Galdieria sulphuraria, and was 147-fold and 12-fold of those in photoautotrophic and heterotrophic technologies, respectively. Therefore, this strategy provides a promising approach for high-efficient phycocyanin production from Galdieria sulphuraria to meet its mass cultivation and commercialization application.

A new technology of CO2 supplementary for microalgae cultivation on large scale - A spraying absorption tower coupled with an outdoor open runway pond.

An effective CO2 supply system of a spraying absorption tower combined with an outdoor ORWP (open raceway pond) for microalgae photoautotrophic cultivation is developed in this paper. The microalgae yield, productivity and CO2 fixation efficiency were investigated, and compared with those of bubbling method. The maximum yield and productivity of biomass were achieved 0.927gL(-1) and 0.114gL(-1)day(-1), respectively. The fixation efficiency of CO2 by microalgae with the spraying tower reached 50%, whereas only 11.17% for bubbling method. Pure CO2 can be used in the spraying absorption tower, and the flow rate was only about one third of the bubbling cultivation. It shows that this new method of quantifiable control CO2 supply can meet the requirements of the growth of microalgae cultivation on large-scale.

Investigation on novel raceway pond with inclined paddle wheels through simulation and microalgae culture experiments.

The open raceway ponds are nowadays the most used large-scale reactors for microalgae culture. To avoid the stacking of microalgae, the paddle wheels are the most widely used to circulate and mix the culture medium. In this paper, a numerical simulation using computational fluid dynamics (CFD) was used to investigate the hydrodynamic characteristics of open raceway ponds with different types of paddle wheels (the traditional paddle wheels and the novel paddle wheels with specially inclined angle of the blades). The particle image velocimetry (PIV) was used to validate the reliability of the CFD model. The CFD simulation results showed that the novel raceway pond with 15° inclined angle of the blades had the best mixing efficiency under the same power consumption. Lastly, the results of microalgae culture experiments showed that the growth rates of Chlorella pyrenoidosa in the novel raceway pond with 15° inclined angle of the blades were higher than those in the traditional reactor. The results of the culture experiments and CFD simulations were identical with each other. Therefore, a novel paddle wheel with 15° inclined angle of the blades was obtained for better microalgae cultivation.

[Pilot-scale purification of lipopeptide from marine-derived Bacillus marinus].

This research was aimed at establishing the pilot-scale purification technology of lipopeptide from marine-derived Bacillus marinus. We studied lipopeptide surfactivity interferences on scale-up unit technologies including acid precipitation, methanol extraction, solvent precipitation, salting out, extraction, silica gel column chromatography and HZ806 macroporous absorption resin column chromatography. Then, the unit technologies were combined in a certain order, to remove the impurities gradually, and to gain purified lipopeptide finally, with high recovery rate throughout the whole process. The novel pilot-scale purification technology could effectively isolate and purify lipopeptide with 87.51% to 100% purity in hectograms from 1 ton of Bacillus marinus B-9987 fermentation broth with more than 81.73% recovery rate. The first practical hectogram production of highly purified lipopeptide derived from Bacillus marinus was achieved. With this new purification method, using complex media became possible in fermentation process to reduce the fermentation cost and scale-up the purification for lipopeptide production. For practicability and economy, foaming problem resulting from massive water evaporation was avoided in this technology.

Genomic Foundation of Starch-to-Lipid Switch in Oleaginous Chlorella spp.

The ability to rapidly switch the intracellular energy storage form from starch to lipids is an advantageous trait for microalgae feedstock. To probe this mechanism, we sequenced the 56.8-Mbp genome of Chlorella pyrenoidosa FACHB-9, an industrial production strain for protein, starch, and lipids. The genome exhibits positive selection and gene family expansion in lipid and carbohydrate metabolism and genes related to cell cycle and stress response. Moreover, 10 lipid metabolism genes might be originated from bacteria via horizontal gene transfer. Transcriptomic dynamics tracked via messenger RNA sequencing over six time points during metabolic switch from starch-rich heterotrophy to lipid-rich photoautotrophy revealed that under heterotrophy, genes most strongly expressed were from the tricarboxylic acid cycle, respiratory chain, oxidative phosphorylation, gluconeogenesis, glyoxylate cycle, and amino acid metabolisms, whereas those most down-regulated were from fatty acid and oxidative pentose phosphate metabolism. The shift from heterotrophy into photoautotrophy highlights up-regulation of genes from carbon fixation, photosynthesis, fatty acid biosynthesis, the oxidative pentose phosphate pathway, and starch catabolism, which resulted in a marked redirection of metabolism, where the primary carbon source of glycine is no longer supplied to cell building blocks by the tricarboxylic acid cycle and gluconeogenesis, whereas carbon skeletons from photosynthesis and starch degradation may be directly channeled into fatty acid and protein biosynthesis. By establishing the first genetic transformation in industrial oleaginous C. pyrenoidosa, we further showed that overexpression of an NAD(H) kinase from Arabidopsis (Arabidopsis thaliana) increased cellular lipid content by 110.4%, yet without reducing growth rate. These findings provide a foundation for exploiting the metabolic switch in microalgae for improved photosynthetic production of food and fuels.

Sequential Heterotrophy-Dilution-Photoinduction Cultivation of Haematococcus pluvialis for efficient production of astaxanthin.

A novel cultivation strategy called "Sequential Heterotrophy-Dilution-Photoinduction" was successfully applied in the cultivation of Haematococcus pluvialis to produce astaxanthin effectively. Cells were first cultivated heterotrophically to achieve a high cell density, then were diluted to a suitable concentration and switched to a favorable environment for cells acclimation. Finally, the culture was transferred to high light environment for astaxanthin accumulation. By this strategy, the dry cell weight of 26 g/L and biomass productivity of 64.1mg/L/h were obtained in heterotrophy stage which surpassed ever before reported in literatures. Meanwhile, the cells could accumulate considerable astaxanthin up to 4.6% of dry cell weight after 10 days of photoinduction. Furthermore, the application prospects of the strategy were confirmed further by outdoor experiments. Therefore, this novel strategy provided a promising approach for high-efficient production of natural astaxanthin from H. pluvialis to meet the huge demand of this high value product.