Metabolite production and growth efficiency

The capacity to sustain the large fluxes of carbon and energy required for rapid metabolite production appears to be inversely related to the growth efficiency of micro-organisms. From an overall energetic point of view three main classes of metabolite may be distinguished. These are not discrete categories, as the energetics of biosynthesis will depend on the precise biochemical pathways used and the nature of the starting feed stock(s). (1) for metabolites like exopolysaccharides both the oxidation state and the specific rate of production appear to be inversely related to the growth efficiency of the producing organism. Maximum rates of production are favored when carbon and energy flux are integrated, and alteration of this balance may negatively effect production rates. (2) The production of metabolites like organic acids and some secondary metabolites results in the net production of reducing equivalents and/or ATP. It is thought that the capacity of the organism to dissipate this product associated energy limits its capacity for rapid production. (3) For metabolites like biosurfactants and certain secondary metabolites that are composed of moieties of significantly different oxidation states production from a single carbon source is unfavorable and considerable improvements in specific production rate and final broth concentration may be achieved if mixed carbon sources are used. By careful selection of production organism and starting feedstock(s) it may be possible to tailor the production, such that the adverse physiological consequences of metabolite overproduction on the production organism are minimized.     

Estimation of phytoplankton production from space: current status and future potential of satellite remote sensing

A new generation of ocean colour satellites is now operational, with frequent observation of the global ocean. This paper reviews the potential to estimate marine primary production from satellite images. The procedures involved in retrieving estimates of phytoplankton biomass, as pigment concentrations, are discussed. Algorithms are applied to SeaWiFS ocean colour data to indicate seasonal variations in phytoplankton biomass in the Celtic Sea, on the continental shelf to the south west of the UK. Algorithms to estimate primary production rates from chlorophyll concentration are compared and the advantages and disadvantage discussed. The simplest algorithms utilise correlations between chlorophyll concentration and production rate and one equation is used to estimate daily primary production rates for the western English Channel and Celtic Sea; these estimates compare favourably with published values. Primary production for the central Celtic Sea in the period April to September inclusive is estimated from SeaWiFS data to be 102 gC m⁻² in 1998 and 93 gC m⁻² in 1999; published estimates, based on in situ incubations, are ca. 80 gC m⁻². The satellite data demonstrate large variations in primary production between 1998 and 1999, with a significant increase in late summer in 1998 which did not occur in 1999. Errors are quantified for the estimation of primary production from simple algorithms based on satellite-derived chlorophyll concentration. These data show the potential to obtain better estimates of marine primary production than are possible with ship-based methods, with the ability to detect short-lived phytoplankton blooms. In addition, the potential to estimate new production from satellite data is discussed.     

Combining genetic engineering and bioprocess concepts for improved phenylpropanoid production

The group of natural aromatic compounds known as phenylpropanoids has diverse applications, but current methods of production which are largely based on synthesis from petrochemicals or extraction from agricultural biomass are unsustainable. Bioprocessing is a promising alternative, but improvements in production titers and rates are required to make this method profitable. Here the recent advances in genetic engineering and bioprocess concepts for the production of phenylpropanoids are presented for the purpose of identifying successful strategies, including adaptive laboratory evolution, enzyme engineering, in-situ product removal, and biocatalysis. The pros and cons of bacterial and yeast hosts for phenylpropanoid production are discussed, also in the context of different phenylpropanoid targets and bioprocess concepts. Finally, some broad recommendations are made regarding targets for continued improvement and areas requiring specific attention from researchers to further improve production titers and rates.     

Fuel ethanol production: process design trends and integration opportunities

Current fuel ethanol research and development deals with process engineering trends for improving biotechnological production of ethanol. In this work, the key role that process design plays during the development of cost-effective technologies is recognized through the analysis of major trends in process synthesis, modeling, simulation and optimization related to ethanol production. Main directions in techno-economical evaluation of fuel ethanol processes are described as well as some prospecting configurations. The most promising alternatives for compensating ethanol production costs by the generation of valuable co-products are analyzed. Opportunities for integration of fuel ethanol production processes and their implications are underlined. Main ways of process intensification through reaction-reaction, reaction-separation and separation-separation processes are analyzed in the case of bioethanol production. Some examples of energy integration during ethanol production are also highlighted. Finally, some concluding considerations on current and future research tendencies in fuel ethanol production regarding process design and integration are presented.     

The greenhouse gas emissions performance of cellulosic ethanol supply chains in Europe

Background  

The production of fuel-grade ethanol from lignocellulosic biomass resources has the potential to increase biofuel production capacity whilst minimising the negative environmental impacts. These benefits will only be realised if lignocellulosic ethanol production can compete on price with conventional fossil fuels and if it can be produced commercially at scale. This paper focuses on lignocellulosic ethanol production in Europe. The hypothesis is that the eventual cost of production will be determined not only by the performance of the conversion process but by the performance of the entire supply-chain from feedstock production to consumption. To test this, a model for supply-chain cost comparison is developed, the components of representative ethanol supply-chains are described, the factors that are most important in determining the cost and profitability of ethanol production are identified, and a detailed sensitivity analysis is conducted.     

固定化技术在促进光合细菌产氢中的应用

氢气是一种新型的清洁高效能源,制氢技术的创新是目前研究的热点。将新型的技术及材料应用到生物制氢工艺中,从而促进生物制氢技术的产氢效率和工程应用是研究的重点之一。该文阐述了光合细菌在固定化生长条件下发酵产氢的最新研究进展,从固定化技术的原理、固定化方法的应用进展及影响因素几个方面进行了综述,详细阐述了包括包埋、悬浮载体附着生长及固定生物膜法等几种固定化方法对光发酵产氢的作用,介绍了国内外用于固定化的新型材料,并对今后的研究重点及方向进行了展望。     

Simultaneous expression of recombinant proteins in the insect cell-baculovirus system: production of virus-like particles

The insect cell-baculovirus system (IC-BEVS) is widely used for the production of recombinant viral proteins for vaccine applications. It is especially suitable for the production of virus-like particles, which often require the simultaneous production of several recombinant proteins. Here, the available tools and process requirements for the simultaneous production of several recombinant proteins using the IC-BEVS are discussed. The production of double-layered rotavirus like particles is used as a specific example for the simultaneous production of two recombinant proteins. Methods to quantify VLP in small samples are described. The multiplicity and time of infection are presented as tools to manipulate protein concentration, and the effect on protein concentration ratios on the assembly efficiency of double-layered rotavirus like particles is discussed. It was found that not only the ratio between the recombinant proteins is determinant of VLP assembly efficiency, but also that assembly efficiency is related to the characteristics of the assembled proteins. This is the first time that kinetics of VLP production are followed during cultures, and that the assembly efficiency is quantitatively determined.     

能源生物技术

对生物技术在能源领域的应用包括燃料酒精、生物柴油、生物制氢及微生物采油技术等的国内外现状进行了综述,对其研究的意义和前景进行了分析。     

The genetic structure of swarms and the timing of their production in the queen cycles of neotropical wasps

Kin selection theory has received some of its strongest support from analyses of within-colony conflicts between workers and queens in social insects. One of these conflicts involves the timing of queen production. In neotropical wasps, new queens are only produced by colonies with just one queen while males are produced by colonies with more queens, a pattern favoured by worker interests. We now show that new colonies, or swarms, have few queens and variable within-colony relatednesses which means that their production is not tied to new queen production. The queens in these swarms are seldom the mothers of the workers in the swarm. Therefore, either colonies producing swarms have very many queens, or queens joining daughter swarms are reproductive losers on the original colonies. As new colony production is not linked to queen production, it can occur at the ecologically optimum time, i.e. the rainy season. This disassociation between queen production and new colony production allows worker interests in sex ratios to prevail without hampering new colony production at the most favourable season, an uncoupling that may contribute to the ecological success of the Epiponini.     

Succinate production in Escherichia coli

Succinate has been recognized as an important platform chemical that can be produced from biomass. While a number of organisms are capable of succinate production naturally, this review focuses on the engineering of Escherichia coli for the production of four-carbon dicarboxylic acid. Important features of a succinate production system are to achieve an optimal balance of reducing equivalents generated by consumption of the feedstock, while maximizing the amount of carbon channeled into the product. Aerobic and anaerobic production strains have been developed and applied to production from glucose and other abundant carbon sources. Metabolic engineering methods and strain evolution have been used and supplemented by the recent application of systems biology and in silico modeling tools to construct optimal production strains. The metabolic capacity of the production strain, the requirement for efficient recovery of succinate, and the reliability of the performance under scaleup are important in the overall process. The costs of the overall biorefinery-compatible process will determine the economic commercialization of succinate and its impact in larger chemical markets.     

草地农业生态系统的碳平衡分析方法

根据草地农业生态系统的结构,它的碳平衡为4个生产层的碳平衡之和,也是3个界面的碳平衡之和,而某一生产层或者某一界面的碳平衡则是其固定、输入、排放和输出的碳之和。草地农业生态系统4个生产层的碳平衡分析方法定量重要生产环节的碳汇与碳源过程,便于草业生产改进碳汇管理;草地农业生态系统3个界面的碳平衡分析方法显示碳源和碳汇的发生机理,及其空间和数量关系,便于调控草业生产组分以增汇减排;但是,这两个方法不易区分碳的来源和去向,难以明确其利用效率。草地农业生态系统碳平衡分析的输入/输出法定量地指示碳的来源和去向,以及碳效率,计算简单,但是较为概括,不利于牧场尺度的草业碳汇管理。以中国祁连山甘肃马鹿牧场和澳大利亚塔斯玛尼亚奶牛牧场为例,用3种方法分析了两个牧场的碳平衡,结果表明,放牧管理的草业系统的主要碳源是休闲旅游、产品加工流通环节产生的温室气体,主要碳汇是草地和土壤中贮存的碳,好的草地管理可以增汇减排。     

Sources of technical efficiency of sheep production systems in dry areas in Syria

A random sample of sheep producers in the dry areas of Syria were surveyed in 2002. Based on sheep movement, four production systems were identified; migratory, transhumance, semi-sedentary and sedentary. The survey data was analyzed using a single-stage model for estimating the technical inefficiencies of each production and its determinants. Technical efficiency ranges from 0.67 to 0.97, with considerable variation within each of the four production systems. The sedentary production system was the most efficient, and the migratory system the least efficient. The major factors causing inefficiencies included high abortion rate, low fertility, high lamb mortality, and long distances to markets and water sources. Improving the physiological conditions of the sheep and selecting the appropriate system of sheep production according to the location of the farm would improve efficiency of the sheep production substantially. Efficiency of sheep production in Syria can be improved by encouraging producers to shift to more intensive systems. As production and market conditions are fairly stable in Syria, the results and their implications are still valid.     

Adaptive Evolution in Producing Microtiter Cultivations Generates Genetically Stable Escherichia coli Production Hosts for Continuous Bioprocessing

The production of recombinant proteins usually reduces cell fitness and the growth rate of producing cells. The growth disadvantage favors faster-growing non-producer mutants. Therefore, continuous bioprocessing is hardly feasible in Escherichia coli due to the high escape rate. The stability of E. coli expression systems under long-term production conditions and how metabolic load triggered by recombinant gene expression influences the characteristics of mutations are investigated. Iterated fed-batch-like microbioreactor cultivations are conducted under production conditions. The easy-to-produce green fluorescent protein (GFP) and a challenging antigen-binding fragment (Fab) are used as model proteins, and BL21(DE3) and BL21^Q strains as expression hosts. In comparative whole-genome sequencing analyses, mutations that allowed cells to grow unhindered despite recombinant protein production are identified. A T7 RNA polymerase expression system is only conditionally suitable for long-term cultivation under production conditions. Mutations leading to non-producers occur in either the T7 RNA polymerase gene or the T7 promoter. The host RNA polymerase-based BL21^Q expression system remains stable in the production of GFP in long-term cultivations. For the production of Fab, mutations in lacI of the BL21^Q derivatives have positive effects on long-term stability. The results indicate that adaptive evolution carried out with genome-integrated E. coli expression systems in microtiter cultivations under industrial-relevant production conditions is an efficient strain development tool for production hosts.     

Consumers can enhance ecosystem productivity and stability in changing environments

There is increasing interest in the impacts of pulsed resource inputs (e.g., seasonal fluctuations in primary production) on ecosystem properties. However, theoretical models have focused on the ecosystem role of consumers only in stable environments. We investigated how the consumption rate affects ecosystem properties when resource supplies are pulsed using a simple model with numerical simulations. We initially investigated how primary production responds to resource supply shortages under various consumption rates and found that a vigorous consumer attenuates a rapid reduction in primary production. We next examined ecosystem properties under pulsed resource supplies. Intermediate consumption enhances primary production. The consumption rate that maximizes productivity differs for producers and consumers in a given resource supply environment, irrespective of the pattern of pulsation. The enhancement of primary production and the maximization of secondary production occur simultaneously in a stable environment but are not always the same when the resource supply is pulsed. We also investigated the variability of primary production and found that intermediate consumption rates reduce its coefficient of variation. In addition, we found that consumers with either very low or very high consumption rates are vulnerable to extinction when resource supplies are pulsed. Therefore, consumers with intermediate consumption rates contribute not only to the enhancement and stabilization of primary production but also to the stability of the consumer population itself.     

Climate change and food security nexus in Asia: A regional comparison

Global climatic conditions are expected to become more variable in the future, which will have far-reaching impacts on food production. In Asia, many of these impacts have been measured, but a comprehensive analysis of the effects of climate change on food production at the regional scale is limited. In this study, two key issues were addressed. First, we estimated the actual trends in temperature and precipitation across 12 Asian countries in Southern, South-Eastern, Western, and Eastern Asia between 1970 and 2018 and examined their implications on food production. Second, we deployed robust estimation techniques and examined how climatic conditions influence food production across Asian sub-regions. The results show that annual temperature across Asian regions trends positively. However, a cross-country analysis reveals varied trends in annual rainfall. The regional results indicate that temperature significantly induces food production in all regions except South-Eastern Asia, where the effect is negligible. Rainfall promotes food production in Southern, South-Eastern, and Western Asia but is not favourable to food production in Eastern Asia. The findings also show that the impacts of climatic variables on food production differ significantly from country to country. Our results are robust and suggest that substantial investments in agricultural extension, research programmes, and improved irrigation infrastructure are critical to enhancing food production and security in Asia.     

甘薯抗线虫病的遗传育种研究

甘薯线虫病是危害甘薯的主要病害,危害甘薯的线虫种类主要是根结线虫和茎线虫.甘薯生产上主要采用综合防治方法进行防治,其中选育抗病品种最为经济有效.本文综述了根结线虫和茎线虫病的抗源筛选、抗性机制、抗性的遗传和抗病育种等方面的研究进展,并展望了甘薯抗线虫病育种.     

Ocean annual phytoplankton carbon and new production,and annual export production estimated with empirical equations and CZCS data

Empirical equations are parameterized for use with chlorophyll a, derived from satellite ocean colour data, to calculate phytoplankton carbon production, phytoplankton new production, and export production. For environments in a high variance (HV) pigment statistical class, annual phytoplankton particulate organic carbon production (AIP) is linearly related to annual average in situ chlorophyll a within the near‐surface layer. Linear relations were also obtained between AIP and annual new nitrogen production, and between AIP and particulate organic carbon annually exported from the euphotic zone for environments in that class. We found no relation between AIP and C_SFC, or between the annual production variables, for oceanic environments characterized by low pigment variance (LV). Ratios of export production to AIP, called e, and new production to nitrogen annually used in phytoplankton production, called f, are widely used to express marine food web processes. The trends of these ratios with AIP differ between HV and LV environments. This is a result of differences in the coupling between nitrogen and carbon transfer in pelagic food webs, which contain different organism size classes in HV compared to LV environments. We applied the empirical equations to CZCS data to estimate global new and export production. The HV environments are responsible for about 40% of global ocean annual phytoplankton carbon production and 70% of global ocean annual new and export production.     

System expansion and allocation in life cycle assessment of milk and beef production

Background, Goal and Scope  System expansion is a method used to avoid co-product allocation. Up to this point in time it has seldom been used in LCA studies of food products, although food production systems often are characterised by closely interlinked sub-systems. One of the most important allocation problems that occurs in LCAs of agricultural products is the question of how to handle the co-product beef from milk production since almost half of the beef production in the EU is derived from co-products from the dairy sector. The purpose of this paper is to compare different methods of handling co-products when dividing the environmental burden of the milk production system between milk and the co-products meat and surplus calves. Main Features  This article presents results from an LCA of organic milk production in which different methods of handling the co-products are examined. The comparison of different methods of co-product handling is based on a Swedish LCA case study of milk production where economic allocation between milk and meat was initially used. Allocation of the co-products meat and surplus calves was avoided by expanding the milk system. LCA data were collected from another case study where the alternative way of producing meat was analysed, i.e. using a beef cow that produces one calf per annum to be raised for one and a half year. The LCA of beef production was included in the milk system. A discussion is conducted focussing on the importance of modelling and analysing milk and beef production in an integrated way when foreseeing and planning the environmental consequences of manipulating milk and beef production systems. Results  This study shows that economic allocation between milk and beef favours the product beef. When system expansion is performed, the environmental benefits of milk production due to its co-products of surplus calves and meat become obvious. This is especially connected to the impact categories that describe the potential environmental burden of biogenic emissions such as methane and ammonia and nitrogen losses due to land use and its fertilising. The reason for this is that beef production in combination with milk can be carried out with fewer animals than in sole beef production systems. Conclusion, Recommendation and Perspective  Milk and beef production systems are closely connected. Changes in milk production systems will cause alterations in beef production systems. It is concluded that in prospective LCA studies, system expansion should be performed to obtain adequate information of the environmental consequences of manipulating production systems that are interlinked to each other.     

Reassessment of inclusion body-based production as a versatile opportunity for difficult-to-express recombinant proteins

The production of recombinant proteins in the microbial host Escherichia coli often results in the formation of cytoplasmic protein inclusion bodies (IBs). Proteins forming IBs are often branded as difficult-to-express, neglecting that IBs can be an opportunity for their production. IBs are resistant to proteolytic degradation and contain up to 90% pure recombinant protein, which does not interfere with the host metabolism. This is especially advantageous for host-toxic proteins like antimicrobial peptides (AMPs). IBs can be easily isolated by cell disruption followed by filtration and/or centrifugation, but conventional techniques for the recovery of soluble proteins from IBs are laborious. New approaches therefore simplify protein recovery by optimizing the production process conditions, and often include mild resolubilization methods that either increase the yield after refolding or avoid the necessity of refolding all together. For the AMP production, the IB-based approach is ideal, because these peptides often have simple structures and are easy to refold. The intentional IB production of almost every protein can be achieved by fusing recombinant proteins to pull-down tags. This review discusses the techniques available for IB-based protein production before considering technical approaches for the isolation of IBs from E. coli lysates followed by efficient protein resolubilization which ideally omits further refolding. The techniques are evaluated in terms of their suitability for the process-scale production and downstream processing of recombinant proteins and are discussed for AMP production as an example.     

碳素和氮素对Coriolus versicolor胞外酶分泌的影响

采用单因子相互比较法研究了不同碳素和氮素对彩绒革盖菌胞外漆酶,愈创木酚氧化酶,多酚氧化酶,锰过氧化物酶等木素降解酶分泌的影响,结果淀粉作碳源,干酪素作氮源有利于漆酶的分泌,麦芽粉作碳源,酵母膏作氮源有利于愈创木酚氧化酶和多酚氧化酶的分泌,淀粉作碳源,玉米粉作氮源有利于锰过氧化物酶的分泌。