Biotechnology and Bioengineering

Thirty microalgal strains were screened in the laboratory for their biomass productivity and lipid content. Four strains (two marine and two freshwater), selected because robust, highly productive and with a relatively high lipid content, were cultivated under nitrogen deprivation in 0.6‐L bubbled tubes. Only the two marine microalgae accumulated lipid under such conditions. One of them, the eustigmatophyte Nannochloropsis sp. F&M‐M24, which attained 60% lipid content after nitrogen starvation, was grown in a 20‐L Flat Alveolar Panel photobioreactor to study the influence of irradiance and nutrient (nitrogen or phosphorus) deprivation on fatty acid accumulation. Fatty acid content increased with high irradiances (up to 32.5% of dry biomass) and following both nitrogen and phosphorus deprivation (up to about 50%). To evaluate its lipid production potential under natural sunlight, the strain was grown outdoors in 110‐L Green Wall Panel photobioreactors under nutrient sufficient and deficient conditions. Lipid productivity increased from 117 mg/L/day in nutrient sufficient media (with an average biomass productivity of 0.36 g/L/day and 32% lipid content) to 204 mg/L/day (with an average biomass productivity of 0.30 g/L/day and more than 60% final lipid content) in nitrogen deprived media. In a two‐phase cultivation process (a nutrient sufficient phase to produce the inoculum followed by a nitrogen deprived phase to boost lipid synthesis) the oil production potential could be projected to be more than 90 kg per hectare per day. This is the first report of an increase of both lipid content and areal lipid productivity attained through nutrient deprivation in an outdoor algal culture. The experiments showed that this marine eustigmatophyte has the potential for an annual production of 20 tons of lipid per hectare in the Mediterranean climate and of more than 30 tons of lipid per hectare in sunny tropical areas. Biotechnol. Bioeng. 2009;102: 100–112. © 2008 Wiley Periodicals, Inc.

Thông tin liên quan đến quá trình thủy phân enzym của cellulose bằng các hệ thống enzyme cellulase không phức tạp được xem xét với trọng tâm đặc biệt về việc phát triển một hiểu biết tổng hợp, bao gồm cả các đặc điểm của cơ chất bên cạnh nồng độ và nhiều thành phần cellulase. Các chủ đề được xem xét bao gồm các đặc tính của cellulose, sự hấp phụ, quá trình thủy phân cellulose và các mô hình định lượng. Một sơ đồ phân loại được đề xuất cho các mô hình định lượng cho quá trình thủy phân enzym của cellulose dựa trên số lượng các hoạt động hòa tan và các biến trạng thái của cơ chất được đưa vào. Chúng tôi cho rằng thời điểm hiện tại là thời điểm thích hợp để xem xét và làm sống lại mô hình chức năng của quá trình thủy phân cellulose, và rằng điều này sẽ mang lại lợi ích lớn, nếu không nói là cần thiết, để kết nối khối lượng thông tin lớn có sẵn về các thành phần cellulase với các ứng dụng chính thúc đẩy sự quan tâm đến chủ đề này. © 2004 Wiley Periodicals, Inc.

General rules for the optimization of different biocatalytic systems in various types of media containing organic solvents are derived by combining data from the literature, and the logarithm of the partition coefficient, log P, as a quantitative measure of solvent polarity. (1) Biocatalysis in organic solvents is low in polar solvents having a log P < 2, is moderate in solvents having a log P between 2 and 4, and is high in a polar solvents having a log P > 4. It was found that this correlation between polarity and activity parallels the ability of organic solvents to distort the essential water layer that stabilizes the biocatalysts. (2) Further optimization of biocatalysis in organic solvents is achieved when the polarity of the microenvironment of the biocatalyst (log P_i) and the continuous organic phase (log P_cph) is tuned to the polarities of both the substrate (log P_s) and the product (log P_p) according to the following rules: |log P_i − log P_s| and |log P_cph − log P_p| should be minimal and |log P_cph − log P_s| and |log P_i − log P_p| should be maximal, with the exception that in the case of substrate inhibition log P_i, should be optimized with respect to log P_s In addition to these simple optimization rules, the future developments of biocatalysis in organic solvents are discussed.

Real‐time polymerase chain reaction (PCR) is a highly sensitive method that can be used for the detection and quantification of microbial populations without cultivating them in anaerobic processes and environmental samples. This work was conducted to design primer and probe sets for the detection of methanogens using a real‐time PCR with the TaqMan system. Six group‐specific methanogenic primer and probe sets were designed. These sets separately detect four orders (Methanococcales, Methanobacteriales, Methanomicrobiales, and Methanosarcinales) along with two families (Methanosarcinaceae and Methanosaetaceae) of the order Methanosarcinales. We also designed the universal primer and probe sets that specifically detect the 16S rDNA of prokaryotes and of the domain Bacteria and Archaea, and which are fully compatible with the TaqMan real‐time PCR system. Target‐group specificity of each primer and probe set was empirically verified by testing DNA isolated from 28 archaeal cultures and by analyzing potential false results. In general, each primer and probe set was very specific to the target group. The primer and probe sets designed in this study can be used to detect and quantify the order‐level (family‐level in the case of Methanosarcinales) methanogenic groups in anaerobic biological processes and various environments. © 2005 Wiley Periodicals, Inc.

In recent years considerable effort has been made in the Netherlands toward the development of a more sophisticated anaerobic treatment process, suitable for treating low a strength wastes and for applications at liquid detention times of 3–4 hr. The efforts have resulted in new type of upflow anaerobic sludge blanket (UASB) process, which in recent 6 m³ pilot‐plant experiments has shown to be capable of handling organic space loads of 15–40 kg chemical oxygen demand (COD)·m⁻³/day at 3–8 hr liquid detention times. In the first 200 m³ full‐scale plant of the UASB concept, organic space loadings of up to 16 kg COD·m⁻³/day could be treated satisfactorily at a detention times of 4 hr, using sugar beet waste as feed. The main results obtained with the process in the laboratory as well as in 6 m³ pilot plant and 200 m³ full‐scale experiments are presented and evaluated in this paper. Special attention is given to the main operating characteristics of the UASB reactor concept. Moreover, some preliminary results are presented of laboratory experiments concerning the use of the USB reactor concept for denitrification as well as for the acid formation step in anaerobic treatment. For both purposes the process looks feasible because very satisfactory results with respect to denitrification and acid formation can be achieved at very high hydraulic loads (12 day⁻¹) and high organic loading rates, i.e., 20 kg COD·m⁻³/day in the denitrification and 60–80 kg COD·m⁻³/day in the acid formation experiments.

A mathematical model is presented for both batch and continuous cultures of microorganisms utilizing inhibitory substrates. The key feature of the model is the use of a inhibition function to relate substrate concentration and specific growth rate. Simulation studies show that the primary result of inhibition by substrate in a batch culture is an increase in the lag time whereas in continuous culture inhibition by substrate may result in process instability. The model should be of value in investigations of the stability of biological processes used for the treatment of certain industrial wastes such as those containing phenols, thiocyanates, nitrates, ammonia, volatile acids, etc., which are known to be inhibitory to many of the organisms metabolizing them.

Silver nanoparticles can be coated on common polyurethane (PU) foams by overnight exposure of the foams to nanoparticle solutions. Repeated washing and air‐drying yields uniformly coated PU foam, which can be used as a drinking water filter where bacterial contamination of the surface water is a health risk. Nanoparticles are stable on the foam and are not washed away by water. Morphology of the foam was retained after coating. The nanoparticle binding is due to its interaction with the nitrogen atom of the PU. Online tests were conducted with a prototypical water filter. At a flow rate of 0.5 L/min, in which contact time was of the order of a second, the output count of Escherichia coli was nil when the input water had a bacterial load of 10⁵ colony‐forming units (CFU) per mL. Combined with the low cost and effectiveness in its applications, the technology may have large implications to developing countries. © 2005 Wiley Periodicals, Inc.

Các hạt gel alginate calci đã được chuẩn bị từ một loạt các alginate đã được đặc trưng tốt. Tính chất vật lý của các hạt phụ thuộc mạnh vào thành phần, cấu trúc tuần tự, và kích thước phân tử của các polymer. Các hạt với độ bền cơ học cao nhất, độ co ngót thấp nhất, độ ổn định tốt nhất đối với các cation đơn hóa trị, và độ xốp cao nhất được tạo ra từ alginate có hàm lượng axit L‐guluronic cao hơn 70% và chiều dài trung bình của các khối G cao hơn 15. Đối với những alginate “g cao” này, độ nhớt nội tại tại điểm trùng lặp quan trọng đã được xác định, và đối với trọng lượng phân tử cao hơn 2,4 × 10⁵, độ bền của gel không phụ thuộc vào trọng lượng phân tử.

With the aim of understanding the contribution of enzymes to the cost of lignocellulosic biofuels, we constructed a techno‐economic model for the production of fungal cellulases. We found that the cost of producing enzymes was much higher than that commonly assumed in the literature. For example, the cost contribution of enzymes to ethanol produced by the conversion of corn stover was found to be $0.68/gal if the sugars in the biomass could be converted at maximum theoretical yields, and $1.47/gal if the yields were based on saccharification and fermentation yields that have been previously reported in the scientific literature. We performed a sensitivity analysis to study the effect of feedstock prices and fermentation times on the cost contribution of enzymes to ethanol price. We conclude that a significant effort is still required to lower the contribution of enzymes to biofuel production costs. Biotechnol. Bioeng. 2012; 109:1083–1087. © 2011 Wiley Periodicals, Inc.