Recent advances in production of succinic acid from lignocellulosic biomass

Production of succinic acid via separate enzymatic hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) are alternatives and are environmentally friendly processes. These processes have attained considerable positions in the industry with their own share of challenges and problems. The high-value succinic acid is extensively used in chemical, food, pharmaceutical, leather and textile industries and can be efficiently produced via several methods. Previously, succinic acid production via chemical synthesis from petrochemical or refined sugar has been the focus of interest of most reviewers. However, these expensive substrates have been recently replaced by alternative sustainable raw materials such as lignocellulosic biomass, which is cheap and abundantly available. Thus, this review focuses on succinic acid production utilizing lignocellulosic material as a potential substrate for SSF and SHF. SSF is an economical single-step process which can be a substitute for SHF — a two-step process where biomass is hydrolyzed in the first step and fermented in the second step. SSF of lignocellulosic biomass under optimum temperature and pH conditions results in the controlled release of sugar and simultaneous conversion into succinic acid by specific microorganisms, reducing reaction time and costs and increasing productivity. In addition, main process parameters which influence SHF and SSF processes such as batch and fed-batch fermentation conditions using different microbial strains are discussed in detail.     

Perspectives on biotechnological applications of archaea

Many archaea colonize extreme environments. They include hyperthermophiles, sulfur-metabolizing thermophiles, extreme halophiles and methanogens. Because extremophilic microorganisms have unusual properties, they are a potentially valuable resource in the development of novel biotechnological processes. Despite extensive research, however, there are few existing industrial applications of either archaeal biomass or archaeal enzymes. This review summarizes current knowledge about the biotechnological uses of archaea and archaeal enzymes with special attention to potential applications that are the subject of current experimental evaluation. Topics covered include cultivation methods, recent achievements in genomics, which are of key importance for the development of new biotechnological tools, and the application of wild-type biomasses, engineered microorganisms, enzymes and specific metabolites in particular bioprocesses of industrial interest.     

Process considerations and economic evaluation of two-step steam pretreatment for production of fuel ethanol from softwood

To increase the overall ethanol yield from softwood, the steam pretreatment stage can be carried out in two steps. The two-step pretreatment process was evaluated from a techno-economic standpoint and compared with the one-step pretreatment process. The production plants considered were designed to utilize spruce as raw material and have a capacity of 200,000 tons/year. The two-step process resulted in a higher ethanol yield and a lower requirement for enzymes. However, the two-step process is more capital-intensive and has a higher energy requirement. The estimated ethanol production cost was the same, 4.13 SEK/L (55.1 cent /L) for both alternatives. For the two-step process different energy-saving options were considered, such as a higher concentration of water-insoluble solids in the filter cake before the second step, and the possibility of excluding the pressure reduction between the steps. The most optimistic configuration, with 50% water-insoluble solids in the filter cake in the feed to the second pretreatment step, no pressure reduction between the pretreatment steps, and 77% overall ethanol yield (0.25 kg EtOH/kg dry wood), resulted in a production cost of 3.90 SEK/L (52.0 cent /L). This shows the potential for the two-step pretreatment process, which, however, remains to be verified in pilot trials.     

Microbial diversity in support of anaerobic biomass valorization

Microbial diversity provides an immense reservoir of functions and supports key steps in maintaining ecosystem balance through matter decomposition processes and nutrient recycling. The use of microorganisms for biomolecule production is now common, but often involves single-strain cultures. In this review, we highlight the significance of using ecosystem-derived microbial diversity for biotechnological researches. In the context of organic matter mineralization, diversity of microorganisms is essential and enhances the degradation processes. We focus on anaerobic production of biomolecules of interest from discarded biomass, which is an important issue in the context of organic waste valorization and processing. Organic waste represents an important and renewable raw material but remains underused. It is commonly accepted that anaerobic mineralization of organic waste allows the production of diverse interesting molecules within several fields of application. We provide evidence that complex and diversified microbial communities isolated from ecosystems, i.e. microbial consortia, offer considerable advantages in degrading complex organic waste, to yield biomolecules of interest. We defend our opinion that this approach is more efficient and offers enhanced potential compared to the approaches that use single strain cultures.     

Two-step process for ketocarotenoid production by a green alga, Chlorococcum sp. strain MA-1

The production of ketocarotenoids (KCs) from Chlorococcum sp. strain MA-1 was investigated by a two-step process. In the first step, 18 g biomass l(-1) was achieved by feeding glucose to the heterotrophic cultures; in the second step, the high-density cultures were treated with light illumination or chemical stress in dark, respectively, to induce KC synthesis. Light-treated cultures could produce 103 mg total KCs l(-1) and 32 mg astaxanthin l(-1), three times higher than those from chemical-treated cultures, in the 10 days of induction. The percentages of individual KCs (hydroxyechinenone, canthaxanthin, adonirubin and astaxanthin) in the total KCs were not markedly influenced by the different stress conditions. The developed two-step process provides a feasible strategy for commercial production of ketocarotenoids by the green microalga, Chlorococcum sp. strain MA-1.     

Yeast flocculation and its biotechnological relevance

Adhesion properties of microorganisms are crucial for many essential biological processes such as sexual reproduction, tissue or substrate invasion, biofilm formation and others. Most, if not all microbial adhesion phenotypes are controlled by factors such as nutrient availability or the presence of pheromones. One particular form of controlled cellular adhesion that occurs in liquid environments is a process of asexual aggregation of cells which is also referred to as flocculation. This process has been the subject of significant scientific and biotechnological interest because of its relevance for many industrial fermentation processes. Specifically adjusted flocculation properties of industrial microorganisms could indeed lead to significant improvements in the processing of biotechnological fermentation products such as foods, biofuels and industrially produced peptides. This review briefly summarises our current scientific knowledge on the regulation of flocculation-related phenotypes, their importance for different biotechnological industries, and possible future applications for microorganisms with improved flocculation properties.     

Enzyme research and applications in biotechnological intensification of biogas production

Biogas technology provides an alternative source of energy to fossil fuels in many parts of the world. Using local resources such as agricultural crop remains, municipal solid wastes, market wastes and animal waste, energy (biogas), and manure are derived by anaerobic digestion. The hydrolysis process, where the complex insoluble organic materials are hydrolysed by extracellular enzymes, is a rate-limiting step for anaerobic digestion of high-solid organic solid wastes. Biomass pretreatment and hydrolysis are areas in need of drastic improvement for economic production of biogas from complex organic matter such as lignocellulosic material and sewage sludge. Despite development of pretreatment techniques, sugar release from complex biomass still remains an expensive and slow step, perhaps the most critical in the overall process. This paper gives an updated review of the biotechnological advances to improve biogas production by microbial enzymatic hydrolysis of different complex organic matter for converting them into fermentable structures. A number of authors have reported significant improvement in biogas production when crude and commercial enzymes are used in the pretreatment of complex organic matter. There have been studies on the improvement of biogas production from lignocellulolytic materials, one of the largest and renewable sources of energy on earth, after pretreatment with cellulases and cellulase-producing microorganisms. Lipids (characterised as oil, grease, fat, and free long chain fatty acids, LCFA) are a major organic compound in wastewater generated from the food processing industries and have been considered very difficult to convert into biogas. Improved methane yield has been reported in the literature when these lipid-rich wastewaters are pretreated with lipases and lipase-producing microorganisms. The enzymatic treatment of mixed sludge by added enzymes prior to anaerobic digestion has been shown to result in improved degradation of the sludge and an increase in methane production. Strategies for enzyme dosing to enhance anaerobic digestion of the different complex organic rich materials have been investigated. This review also highlights the various challenges and opportunities that exist to improve enzymatic hydrolysis of complex organic matter for biogas production. The arguments in favor of enzymes to pretreat complex biomass are compelling. The high cost of commercial enzyme production, however, still limits application of enzymatic hydrolysis in full-scale biogas production plants, although production of low-cost enzymes and genetic engineering are addressing this issue.     

Enzyme research and applications in biotechnological intensification of biogas production

Biogas technology provides an alternative source of energy to fossil fuels in many parts of the world. Using local resources such as agricultural crop remains, municipal solid wastes, market wastes and animal waste, energy (biogas), and manure are derived by anaerobic digestion. The hydrolysis process, where the complex insoluble organic materials are hydrolysed by extracellular enzymes, is a rate-limiting step for anaerobic digestion of high-solid organic solid wastes. Biomass pretreatment and hydrolysis are areas in need of drastic improvement for economic production of biogas from complex organic matter such as lignocellulosic material and sewage sludge. Despite development of pretreatment techniques, sugar release from complex biomass still remains an expensive and slow step, perhaps the most critical in the overall process. This paper gives an updated review of the biotechnological advances to improve biogas production by microbial enzymatic hydrolysis of different complex organic matter for converting them into fermentable structures. A number of authors have reported significant improvement in biogas production when crude and commercial enzymes are used in the pretreatment of complex organic matter. There have been studies on the improvement of biogas production from lignocellulolytic materials, one of the largest and renewable sources of energy on earth, after pretreatment with cellulases and cellulase-producing microorganisms. Lipids (characterised as oil, grease, fat, and free long chain fatty acids, LCFA) are a major organic compound in wastewater generated from the food processing industries and have been considered very difficult to convert into biogas. Improved methane yield has been reported in the literature when these lipid-rich wastewaters are pretreated with lipases and lipase-producing microorganisms. The enzymatic treatment of mixed sludge by added enzymes prior to anaerobic digestion has been shown to result in improved degradation of the sludge and an increase in methane production. Strategies for enzyme dosing to enhance anaerobic digestion of the different complex organic rich materials have been investigated. This review also highlights the various challenges and opportunities that exist to improve enzymatic hydrolysis of complex organic matter for biogas production. The arguments in favor of enzymes to pretreat complex biomass are compelling. The high cost of commercial enzyme production, however, still limits application of enzymatic hydrolysis in full-scale biogas production plants, although production of low-cost enzymes and genetic engineering are addressing this issue.     

Perspectives of biotechnological production of <Emphasis Type="SmallCaps">l</Emphasis>-ribose and its purification

l-Ribose is a non-natural and expensive sugar that can be used as an important intermediate for the synthesis of l-nucleoside analogues, which are used as antiviral drugs. In contrast to chemical production, biotechnological methods can produce l-ribose from biomass under environmentally friendly conditions. In this mini-review, various strategies for synthesizing l-ribose by applying microorganisms and their enzymes are discussed, including microbial biotransformation and biocatalysis by engineering bacteria. Furthermore, subsequent isolation-and-purification techniques, as an integral step in the whole process, are accordingly described, containing the especial introduction of a promising strategy of l-ribose separation. Particularly, further researches and outlook for the improvement of l-ribose preparation was solely stressed. Compared with each method, this mini-review provides a panorama of respective advantages and disadvantages existing in them.     

Metabolic engineering of bacteria

Yield and productivity are critical for the economics and viability of a bioprocess. In metabolic engineering the main objective is the increase of a target metabolite production through genetic engineering. Metabolic engineering is the practice of optimizing genetic and regulatory processes within cells to increase the production of a certain substance. In the last years, the development of recombinant DNA technology and other related technologies has provided new tools for approaching yields improvement by means of genetic manipulation of biosynthetic pathway. Industrial microorganisms like Escherichia coli, Actinomycetes, etc. have been developed as biocatalysts to provide new or to optimize existing processes for the biotechnological production of chemicals from renewable plant biomass. The factors like oxygenation, temperature and pH have been traditionally controlled and optimized in industrial fermentation in order to enhance metabolite production. Metabolic engineering of bacteria shows a great scope in industrial application as well as such technique may also have good potential to solve certain metabolic disease and environmental problems in near future.     

L-核糖的生产研究进展

L-核糖是合成许多抗病毒药物的关键中间体,自然界和生物体中并不存在。L-核糖的制备方法有化学合成法和生物合成法。与化学合成法相比,生物合成法对环境更加有利。生物合成法是应用微生物及其酶以核糖醇或L-阿拉伯糖为原料生产L-核糖。综述了L-核糖的制备方法以及产品的分离纯化技术,并对L-核糖的研究现状和前景进行了展望。     

Mineral-microbe interactions: biotechnological potential of bioweathering

Mineral-microbe interaction has been a key factor shaping the lithosphere of our planet since the Precambrian. Detailed investigation has been mainly focused on the role of bioweathering in biomining processes, leading to the selection of highly efficient microbial inoculants for the recovery of metals. Here we expand this scenario, presenting additional applications of bacteria and fungi in mineral dissolution, a process with novel biotechnological potential that has been poorly investigated. The ability of microorganisms to trigger soil formation and to sustain plant establishment and growth are suggested as invaluable tools to counteract the expansion of arid lands and to increase crop productivity. Furthermore, interesting exploitations of mineral weathering microbes are represented by biorestoration and bioremediation technologies, innovative and competitive solutions characterized by economical and environmental advantages. Overall, in the future the study and application of the metabolic properties of microbial communities capable of weathering can represent a driving force in the expanding sector of environmental biotechnology.     

Recent development of advanced biotechnology for wastewater treatment

Abstract

The importance of highly efficient wastewater treatment is evident from aggravated water crises. With the development of green technology, wastewater treatment is required in an eco-friendly manner. Biotechnology is a promising solution to address this problem, including treatment and monitoring processes. The main directions and differences in biotreatment process are related to the surrounding environmental conditions, biological processes, and the type of microorganisms. It is significant to find suitable biotreatment methods to meet the specific requirements for practical situations. In this review, we first provide a comprehensive overview of optimized biotreatment processes for treating wastewater during different conditions. Both the advantages and disadvantages of these biotechnologies are discussed at length, along with their application scope. Then, we elaborated on recent developments of advanced biosensors (i.e. optical, electrochemical, and other biosensors) for monitoring processes. Finally, we discuss the limitations and perspectives of biological methods and biosensors applied in wastewater treatment. Overall, this review aims to project a rapid developmental path showing a broad vision of recent biotechnologies, applications, challenges, and opportunities for scholars in biotechnological fields for “green” wastewater treatment.     

Enzyme stability in downstream processing. Part 2: quantification of inactivation

In biotechnological recovery processes the instability of the product can lead to large losses in the sequence of recovery processes needed to purify the product. As the cost of the final active product is strongly dependent on the recovery yield, this will lead to an increase in product cost. Therefore knowledge of factors that influence stability is important. This Part 2 provides the basic principles for design and operation of processes in which inactivation takes place. Simple kinetics and reactor modelling are discussed. These are applied to a number of unit operations: cell disruption, membrane filtration, drying and reversed micellar extraction. It is thus shown that the basic tools for modeling of biochemical processes provide us with the data needed for optimal process design and operation.     

Principles for optimizing and guaging several processes in the technology of vaccine production. II. Modeling processes of thermal inactivation of microorganisms]

The paper treats of some problems pertinent to modelling of thermal inactivation of the microbes serving as a theoretical foundation for the achievement of guaranteed sterility of the equipment, communications and fluids. The principal attention is devoted to the problems of quantitative assessment of the efficacy of the mentioned processes. The advantages and the drawbacks of some deterministic and probability models which found application in microbiological laboratories are assessed. The expediency of orientation on a model proposing the use of characteristics of thermal resistance of the microorganisms and considering the heterogeneity of the actual populations by the thermoresistance index was demonstrated.     

Biomass measurement online: the performance of in situ measurements and software sensors

Biomass measurement is one of the most critical measurements in biotechnological processes. The technologies developed for the measurement of biomass in situ have developed over the years. Because it has been over 10 years since the last review concentrating on practical issues concerning biomass measurements, it is time to evaluate recent developments in the field. This review concentrates on the applications of dielectric spectroscopy, optical density, infrared spectroscopy, and fluorescence for in situ measurement of biomass. The advantages offered by these methods and an economic way of estimating biomass concentration, the software sensors, are considered.     

Process characterization strategy for a precipitation step for host cell protein reduction

Process characterization using QbD approaches has rarely been described for precipitation steps used for impurity removal in biopharmaceutical processes. We propose a two-step approach for process characterization in which the first step focuses on product quality and the second focuses on process performance. This approach provides an efficient, streamlined strategy for the characterization of precipitation steps under the Quality by Design paradigm. This strategy is demonstrated by a case study for the characterization of a precipitation using sodium caprylate to reduce host cell proteins (HCP) during a monoclonal antibody purification process. Process parameters were methodically selected through a risk assessment based on prior development data and scientific knowledge described in the literature. The characterization studies used two multivariate blocks to decouple and distinguish the impact of product quality (e.g., measured HCP of the recovered product from the precipitation) and process performance (e.g., step yield). Robustness of the precipitation step was further demonstrated through linkage studies across the overall purification process. HCP levels could be robustly reduced to ≤100 ppm in the drug substance when the precipitation step operated within an operation space of ≤1% (m/v) sodium caprylate, pH 5.0–6.0, and filter flux ≤300 L/m²-hr for a load HCP concentration up to 19,000 ppm. This two-step approach for characterization of precipitation steps has several advantages, including tailoring of the experimental design and scale-down model to the intended purpose for each step, use of a manageable number of experiments without compromising scientific understanding, and limited time and material consumption.     

A perspective on the biotechnological potential of extremophiles.

It is well recognized that many environments considered by man to be extreme are colonized by microorganisms which are specifically adapted to these ecological niches. A diverse range of bacteria, cyanobacteria, algae and yeasts have been isolated from such habitats and it is now widely accepted that these microorganisms provide a valuable resource not only for exploitation in novel biotechnological processes but also as models for investigating how biomolecules are stabilized when subjected to extreme conditions. This short review summarizes our current state of knowledge of this unique group of microorganisms and their enzymes, and attempts to identify their future biotechnological potential.     

Production of high amounts of 3-hydroxypropionaldehyde from glycerol by Lactobacillus reuteri with strongly increased biocatalyst lifetime and productivity

3-hydroxypropionaldehyde (3HPA) is a promising versatile substance derived from the renewable feedstock glycerol. It is a product of glycerol metabolism in Lactobacillus reuteri. Because of toxic effects, the biotechnological production is poor. In this work the biocatalyst lifetime and product formation could be drastically increased. In the established two-step process already applied, cells are grown in the first step under anaerobic conditions, and in the second step the immobilised or suspended biocatalyst is used for 3HPA-production under strict anaerobic conditions. In the first step it was possible to reach a biomass concentration of 5.5g CDW/L (OD(600)≈23.4). In the second step, normally, 3HPA accumulates to a toxic concentration and the reaction stops in less than 60min because of the interaction of 3HPA with cell components. To prevent this, the toxic product is bound to the newly found scavenger carbohydrazide to form the hydrazone. For the first time it was possible to recycle the immobilised biocatalyst for at least ten cycles (overall life time>33hours) in a repeated batch biotransformation with an overall production of 67g 3HPA. The optimal pH-value was between 6.8 and 7.2 at an optimal temperature of 40-45°C. In a single batch biotransformation with suspended resting cells it was possible to produce 150g/L 3HPA as carbohydrazone at an overall productivity of 10.7gL(-1)hours(-1). In a single fed-batch biotransformation at 45°C 138g/L glycerol was converted into 108g/L 3HPA with an overall productivity of 21.6gL(-1)hours(-1). This is the highest 3HPA concentration and productivities reported so far for the microbial production of 3HPA from glycerol.