Microbial lipids from renewable resources: production and characterization

A number of microorganisms belonging to the genera of algae, yeast, bacteria, and fungi have ability to accumulate neutral lipids under specific cultivation conditions. The microbial lipids contain high fractions of polyunsaturated fatty acids and have the potential to serve as a source of significant quantities of transportation fuels. This paper reviews the current state of the art of this field. It summarizes the various microorganism used, feed stocks available, environmental factors that influence growth of cells and accumulation of lipids, major fatty acid composition of lipids, and the technology.     

Bio-based surfactants: enzymatic functionalization and production from renewable resources

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Balancing exploitation of renewable resources by a robot swarm

Renewable resources like fish stock or forests should be exploited at a rate that supports regeneration and sustainability—a complex problem that requires adaptive approaches to maintain a sufficiently high exploitation while avoiding depletion. In the presence of oblivious agents that cannot keep track of all available resources—a frequent condition in swarm robotics—ensuring that the exploitation effort is correctly balanced is particularly challenging. Additionally, the possibility to exploit resources by multiple robots opens the way to focusing the effort either on a single or on multiple resources in parallel. This means that the swarm needs to collectively decide whether to remain cohesive or split among multiple resources, as a function of the ability of the available resources to replenish after exploitation. In this paper, we propose a decentralised strategy for a swarm of robots that adapts to the available resources and balances the effort among them, hence allowing to maximise the exploitation rate while avoiding to completely deplete the resources. A detailed analysis of the strategy parameters provides insights into the working principles and expected performance of the robot swarm.     

Rhamnolipids as biosurfactants from renewable resources: Concepts for next-generation rhamnolipid production

Several microorganisms are known to produce a wide variety of surface-active substances, which are referred to as biosurfactants. Interesting examples for biosurfactants are rhamnolipids, glycolipids mainly known from Pseudomonas aeruginosa produced during cultivation on different substrates like vegetable oils, sugars, glycerol or hydrocarbons. However, besides costs for downstream processing of rhamnolipids, relatively high raw-material prices and low productivities currently inhibit potential economical production of rhamnolipids on an industrial scale. This review focuses on cost-effective and sustainable production of rhamnolipids by introducing new possibilities and strategies regarding renewable substrates. Additionally, past and recent production strategies using alternative substrates such as agro-industrial byproducts or wastes are summarized. Requirements and concepts for next-generation rhamnolipid producing strains are discussed and potential targets for strain-engineering are presented. The discussion of potential new strategies is supported by an analysis of the metabolism of different Pseudomonas species. According to calculations of theoretical substrate-to-product conversion yields and current world-market price analysis, different renewable substrates are compared and discussed from an economical point of view. A next-generation rhamnolipid producing strain, as proposed within this review, may be engineered towards reduced formation of byproducts, increased metabolic spectrum, broadened substrate spectrum and controlled regulation for the induction of rhamnolipid synthesis.     

Industrial bioconversion of renewable resources as an alternative to conventional chemistry

There are numerous possibilities for replacing chemical techniques with biotechnological methods based on renewable resources. The potential of biotechnology (products, technologies, metabolic pathways) is for the most part well known. Often the costs are still the problem. Biotechnological advances have the best chances for replacing some fine chemicals. While the raw material costs are less of a consideration here, the environmental benefit is huge, as chemical-technical processes often produce a wide range of undesirable/harmful by-products or waste. In the case of bulk chemicals (<US $1/kg) the product price is affected mainly by raw material costs. As long as fossil raw materials are still relatively inexpensive, alternatives based on renewable resources cannot establish themselves. Residues and waste, which are available even at no cost in some cases, are an exception. The introduction of new technologies for the efficient use of such raw materials is currently being promoted. The utilisation of residual wood, plant parts, waste fat, and crude glycerol, for example, provides great potential. For industrial chemicals (US $2–4/kg), process and recovery costs play a greater role. Here, innovative production technologies and product recovery techniques (e.g. on-line product separation) can increase competitiveness.     

The utilization of renewable resources in German industrial production

Renewable resources will be an increasingly important issue for the chemical industry in the future. In the context of white biotechnology, they represent the intersection point of agriculture and the chemical industry. The scarcity and related increase in the price of fossil resources make renewable resources an interesting alternative. If one considers the production of bulk chemicals, it is evident that for this area besides the C sources, sugar and starch, new sources of raw materials must be opened up. One possible solution is to utilize lignocellulose both for materials and energy. This article discusses this interesting prospective for the future, particularly from the point of view of the German industry.     

Factors affecting the fermentative lactic acid production from renewable resources(1)

Parameters affecting the fermentative lactic acid (LA) production are summarized and discussed: microorganism, carbon- and nitrogen-source, fermentation mode, pH, and temperature. LA production is compared in terms of LA concentration, LA yield and LA productivity. Also by-product formation and LA isomery are discussed.     

Non-biodegradable biopolymers from renewable resources: perspectives and impacts

In recent years the biotechnological production of bulk biopolymers has focused on the synthesis of biodegradable polymers to replace their non-biodegradable counterparts derived from fossil resources. Examples include polyhydroxyalkanoates and polylactic acid, which act as substitutes for polyolefins. By contrast, the biotechnological production of non-biodegradable polymers from renewable resources has so far been scarcely considered, probably because this idea contradicts the paradigm that all natural compounds are biodegradable. Polythioesters, which were recently described as new biopolymers, do not follow this paradigm because although they are produced by bacteria, they are persistent to microbial degradation. Mankind has a need for both non-biodegradable and biodegradable polymers and methods to produce them from renewable resources will be of great value.     

Dekkera/Brettanomyces yeasts for ethanol production from renewable sources under oxygen-limited and low-pH conditions

Industrial fermentation of lignocellulosic hydrolysates to ethanol requires microorganisms able to utilise a broad range of carbon sources and generate ethanol at high yield and productivity. D. bruxellensis has recently been reported to contaminate commercial ethanol processes, where it competes with Saccharomyces cerevisiae [4, 26]. In this work Brettanomyces/Dekkera yeasts were studied to explore their potential to produce ethanol from renewable sources under conditions suitable for industrial processes, such as oxygen-limited and low-pH conditions. Over 50 strains were analysed for their ability to utilise a variety of carbon sources, and some strains grew on cellobiose and pentoses. Two strains of D. bruxellensis were able to produce ethanol at high yield (0.44 g g⁻¹ glucose), comparable to those reported for S. cerevisiae. B. naardenensis was shown to be able to produce ethanol from xylose. To obtain ethanol from synthetic lignocellulosic hydrolysates we developed a two-step fermentation strategy: the first step under aerobic conditions for fast production of biomass from mixtures of hexoses and pentoses, followed by a second step under oxygen limitation to promote ethanol production. Under these conditions we obtained biomass and ethanol production on synthetic lignocellulosic hydrolysates, with ethanol yields ranging from 0.2 to 0.3 g g⁻¹ sugar. Hexoses, xylose and arabinose were consumed at the end of the process, resulting in 13 g l⁻¹ of ethanol, even in the presence of furfural. Our studies showed that Brettanomyces/Dekkera yeasts have clear potential for further development for industrial processes aimed at production of ethanol from renewable sources.     

Biotechnological production of enantiomeric pure lactic acid from renewable resources: recent achievements, perspectives, and limits

Lactic acid (LA) is an important and versatile chemical that can be produced from renewable resources such as biomass. LA is used in the food, pharmaceutical, and polymers industries and is produced by microorganism fermentation; however, most microorganisms cannot directly utilize biomass such as starchy materials and cellulose. Here, we summarize LA production using several kinds of genetically modified microorganisms, such as LA bacteria, Escherichia coli, Corynebacterium glutamicum, and yeast. Using gene manipulation and metabolic engineering, the yield and optical purity of LA produced from biomass has been significantly improved. In this review, the drawbacks as well as improvements of LA production by fermentation is discussed.     

生物制品研制开发动态

本概述了近年来生物制品研制领域的新动态,包括１９９９年我国新药研制相关法规的修订、有军事背景的生物制品的开发和研制,及在生物药物研制中值得重视的新生物技术领域。另外,介绍了生物制品的知识产权保护情况及如何查找生物技术专利资源。     

Enzymatic synthesis and curing of polycardol from renewable resources

For the first time, oxidative polymerization of cardol derived from cashew nut shell liquid (CNSL), which is a cheap, useful, and renewable substance, has been carried out using a fungal peroxidase from Coprinus cinereus (CiP). Cardol, one of the major components of CNSL, is a resorcinol derivative mainly having a C15 unsaturated hydrocarbon chain with 1–3 double bonds at a meta position. To date cardol has not been completely exploited as a monomer for enzymatic polymerization. Enzymatic polymerization of cardol proceeded with higher yield in an equivolume mixture of tert-butanol and phosphate buffer (pH 7.0). The yield and molecular weight of polycardol depended on the hydrogen peroxide concentration. Polycardol was rapidly cured at room temperature within 4 h to give harden dry and dark brown color coatings. Pencil scratch hardness data indicated that the curing rate of polycardol was superior to those of polycardanol. Thermogravimetric analysis implied that the cured product from polycardol was thermally more stable than that from polycardanol. We expect that polycardol from renewable resources, which is similar to or superior to polycardanol, can find many applications in the near future.     

Bionanocomposites from renewable resources: epoxidized linseed oil-polyhedral oligomeric silsesquioxanes hybrid materials

This study is concerned with the preparation and properties of a new class of bionanocomposites from renewable resources. Epoxidized linseed oil (ELO) and 3-glycidylpropylheptaisobutyl-T8-polyhedral oligomeric silsesquioxane (G-POSS) (2, 5, and 10 wt %) were cross-linked, and Fourier transform infrared spectroscopy (FTIR), dynamic mechanical thermal analysis (DMTA), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) were employed to characterize the POSS-reinforced oil-based polymer networks. No POSS aggregates were observed for the 2 wt % G-POSS nanocomposite by SEM. POSS-rich particles with diameters of several nanometers were observed in the nanocomposites with 5 and 10 wt % G-POSS. Enhanced glass transition temperatures and storage moduli of the networks in the glassy state and rubber plateau were observed to be higher than those of the POSS-free oil based polymer network, due to the reinforcement effect of POSS cages.     

Wastewater use in algae production for generation of renewable resources: a review and preliminary results

Microalgae feedstock production can be integrated with wastewater and industrial sources of carbon dioxide. This study reviews the literature on algae grown on wastewater and includes a preliminary analysis of algal production based on anaerobic digestion sludge centrate from the Howard F. Curren Advanced Wastewater Treatment Plant (HFC AWTP) in Tampa, Florida and secondary effluent from the City of Lakeland wastewater treatment facilities in Lakeland, Florida. It was demonstrated that a mixed culture of wild algae species could successfully be grown on wastewater nutrients and potentially scaled to commercial production. Algae have demonstrated the ability to naturally colonize low-nutrient effluent water in a wetland treatment system utilized by the City of Lakeland. The results from these experiments show that the algae grown in high strength wastewater from the HFC AWTP are light-limited when cultivated indoor since more than 50% of the outdoor illumination is attenuated in the greenhouse. An analysis was performed to determine the mass of algae that can be supported by the wastewater nutrients (mainly nitrogen and phosphorous) available from the two Florida cities. The study was guided by the growth and productivity data obtained for algal growth in the photobioreactors in operation at the University of South Florida. In the analysis, nutrients and light are assumed to be limited, while CO₂ is abundantly available. There is some limitation on land, especially since the HFC AWTP is located at the Port of Tampa. The temperature range in Tampa is assumed to be suitable for algal growth year round. Assuming that the numerous technical challenges to achieving commercial-scale algal production can be met, the results presented suggest that an excess of 71 metric tons per hectare per year of algal biomass can be produced. Two energy production options were considered; liquid biofuels from feedstock with high lipid content, and biogas generation from anaerobic digestion of algae biomass. The total potential oil volume was determined to be approximately 337,500 gallons per year, which may result in the annual production of 270,000 gallons of biodiesel when 80% conversion efficiency is assumed. This production level would be able to sustain approximately 450 cars per year on average. Potential biogas production was estimated to be above 415,000 kg/yr, the equivalent of powering close to 500 homes for a year.     

Industrial yeast strain engineered to ferment ethanol from lignocellulosic biomass

In this study an industrial Saccharomyces cerevisiae yeast strain capable of fermenting ethanol from pretreated lignocellulosic material was engineered. Genes encoding cellulases (endoglucanase, exoglucanase and β-glucosidase) were integrated into the chromosomal ribosomal DNA and delta regions of a derivative of the K1-V1116 wine yeast strain. The engineered cellulolytic yeast produces ethanol in one step through simultaneous saccharification and fermentation of pretreated biomass without the addition of exogenously produced enzymes. When ethanol fermentation was performed with 10% dry weight of pretreated corn stover, the recombinant strain fermented 63% of the cellulose in 96 h and the ethanol titer reached 2.6% v/v. These results demonstrate that cellulolytic S. cerevisiae strains can be used as a platform for developing an economical advanced biofuel process.     

Gelidium commercial exploitation: natural resources and cultivation

The state of the Gelidium agarophyte resource was last reviewed in 1990 during the First International Workshop on Gelidium. The main objective of the present study was to gather and analyse the new information made available since then, with emphasis on the G. sesquipedale resource from the Iberian Peninsula and Morocco. Other Gelidium-based resources world-wide are also reviewed, as well as new attempts to cultivate Gelidium species in the sea. In general, since the late 1980s, G. sesquipedale yields have decreased in Portugal, and increased in Spain and Morocco. Current reported values, in dry weights, are ca. 670 t yr-1 for Portugal (average 1995–1997), 5200 t yr-1 in Spain, and 6950 t yr-1 for Morocco (average 1994–1996). Efforts to develop cultivation of G. sesquipedale in the sea in Spain have yet to progress beyond the demonstration scale. Other important Gelidium-based agarophyte resources are located in: (i) South Africa where, in addition to G. pristoides, new species are being harvested, with total agarophyte landings of 140 t yr-1 in 1996; (ii) Mexico, where G. robustum harvest averaged 750 t yr-1 in 1987–1996; (iii) and Chile where harvest of Gelidium species yielded ca. 460 t yr-1 in 1990–1992. Preliminary research on new techniques for commercial cultivation of Gelidium species is also reported from these countries. This revised version was published online in June 2006 with corrections to the Cover Date.