Chitin and Chitosan: Sustainable, Medically Relevant Biomaterials

The polysaccharides chitin and chitosan are made up of monomer units of the amino sugars D-glucosamine and N-acetyl-D-glucosamine. The ratio of these two monomers dictates whether the polysaccharide is considered chitin or chitosan. Both polymers have unique properties and have uses in several diverse applications. In nature, chitin and chitosan primarily play a structural role. When purified from their producing organism, these polymers exhibit useful structural, chemical and biological properties. Chitin and chitosan have been used in several applications including biomedicine, food additives, cosmetics, and more. The charged chitosan polymer is especially effective in biomedical applications, as it has been demonstrated to possess antimicrobial properties. This review explores the properties of chitin and chitosan and how these biopolymers are used in a variety of healthcare and other applications

From Beverages to Biofuels: The Journeys of Ethanol-Producing Microorganisms

Microbial fermentation for bio-based products is quickly becoming an integral component of the world infrastructure, as the processes encompassing the synthesis of these natural products becomes more efficient and cost effective to compete with existing commodities. Bioethanol is currently one of the most desired fermentation products, as this constituent can be applied to multiple uses in not only contributing to the more traditional routes of beer brewing and winemaking, but also in the foundation for green fuel sources. By optimizing yields, the innovative processes could be applied towards engineering more rapid and productive biomanufacturing. In order to achieve these goals, we as researchers must understand the underlying principles and intricate networks that play a role within the microenvironment and also on the cellular level in key fermentative microbes such as Saccharomyces cerevisiae and Zymomonas mobilis. In-depth pathway analysis could lead to the development of more favorable metabolic outcomes. This review focuses on the key metabolic networks and cellular frameworks in these model organisms, and how biosynthesis of ethanol yields can be optimized throughout the fermentation process

Applications of Polyhydroxyalkanoates in the Medical Industry

The bio-based, biodegradable family of polymers, polyhydroxyalkanoates (PHA), is an attractive candidate for an environmentally friendly replacement of petroleum-based plastics in many applications. In the past decade, many groups have examined the biodegradability and biocompatibility of PHA in cell culture systems or in an animal host. Findings suggest that PHA is a suitable material for fabrication of resorbable medical devices, such as sutures, meshes, implants, and tissue engineering scaffolds. The degradation kinetics of some PHA polymers is also suggestive of drug release applications. In this review, we examine the progress, potential applications, challenges and outlook in the medical polyhydroxyalkanoate field

The Potential of Polyhydroxyalkanoate Production from Food Wastes

Background and objective: Over 1 billion tons of foods are wasted every year (not consumed by humans or animals). Most of this waste ends up in landfills. As the global population increases, mankind must look for more sustainable means of living. A recently popular idea is the use of organic wastes as carbon feedstocks for fermentation that produces value added products. Polyhydroxyalkanoates are a family of bio-based, biodegradable polymers that can be produced in large quantities using food and food processing wastes as the main feedstocks. In many cases, biocatalysts have been engineered to efficiently use these waste compounds to produce large quantities of useful intracellular polyhydroxyalkanoates.Results and conclusion: In the current study, various polyhydroxyalkanoates were produced; each with different thermal and mechanical characteristics useful for different applications. If polyhydroxyalkanoate production facilities are established next to food waste accumulation sites (e.g., large landfills), potentials for the economical and sustainable polyhydroxyalkanoate production sound promising.Conflict of interest: The authors declare no conflict of interest

Chitin Extraction from Lobster Shell Waste using Microbial Culture-based Methods

Background and Objective: Lobster shell waste from seafood processing industry was used as the source of raw material to produce the valuable biopolymer chitin. Chemical and biological treatments of lobster shell waste were performed and compared.Material and Methods: The chemical method required the use of aqueous solutions of HCl and NaOH. Biological treatment included the use of co-cultures with a protease-producing bacterium, either Bacillus megaterium NH21 or Serratia marcescens db11, and an organic acid-producing bacterium Lactobacillus plantarum. The optimal culture conditions, including co-cultivation strategies and glucose concentrations, were identified to improve efficiency of lobster shell deproteinization and demineralization.Results and Conclusion: Overall, the successive treatment with a combination of Serratia marcescens db11 and Lactobacillus plantarum resulted in the best co-removal of CaCO3 and proteins and chitin yield (82.56%) from lobster shell biomass, with total deproteinization of 87.19% and total demineralization of 89.59%. The results from the proof-of-concept study described here suggest that microbial treatment may be an environmentally friendly alternative to the chemical method of chitin extraction

Tax Policy and Economic Development: A Roundtable Assessment

Economic development continues to be a top policy issue for the state of Maine. Within the broad topic of economic development is the issue of tax policy, and the state continues to experiment with changes in traditional taxes, such as sales and income, as well as with newer approaches, such as Employment Tax Increment Financing. What works and what does not work? Can the state afford the potential loss of revenues associated with tax incentives? Who wins and who loses from these policies? To answer these questions, Maine Policy Review convened a panel of experts to review Maine’s record. Two represent state government and have been involved directly in the administration of tax incentives, Brian Mahany and Alan P. Brigham. They are joined by two policy analysts with expertise in economic development, Christopher Kit St. John and Charles Colgan. There is a surprising degree of consensus about the inevitability of tax incentives and the value of their judicious application. Yet, it also is clear that they are not the centerpiece of economic development policy, and their impacts on the equitable distribution of public funds must be monitored

Biosynthesis and characterization of polyhydroxyalkanoate containing high 3-hydroxyhexanoate monomer fraction from crude palm kernel oil by recombinant Cupriavidus necator

The potential of plant oils as sole carbon sources for production of P(3HB-co-3HHx) copolymer containing a high 3HHx monomer fraction using the recombinant Cupriavidus necator strain Re2160/pCB113 has been investigated. Various types and concentrations of plant oils were evaluated for efficient conversion of P(3HB-co-3HHx) copolymer. Crude palm kernel oil (CPKO) at a concentration of 2.5 g/L was found to be most suitable for production of copolymer with a 3HHx content of approximately 70 mol%. The time profile of these cells was also examined in order to study the trend of 3HHx monomer incorporation, PHA production and PHA synthase activity. [superscript 1]H NMR and [superscript 13]C NMR analyses confirmed the presence of P(3HB-co-3HHx) copolymer containing a high 3HHx monomer fraction, in which monomers were not randomly distributed. The results of various characterization analyses revealed that the copolymers containing a high 3HHx monomer fraction demonstrated soft and flexible mechanical properties.Malaysia. Ministry of Science, Technology and Innovation (MOSTI Techno Fund)Universiti Sains Malaysia (USM Fellowship

Flexibility in Animal Signals Facilitates Adaptation to Rapidly Changing Environments

Charles Darwin posited that secondary sexual characteristics result from competition to attract mates. In male songbirds, specialized vocalizations represent secondary sexual characteristics of particular importance because females prefer songs at specific frequencies, amplitudes, and duration. For birds living in human-dominated landscapes, historic selection for song characteristics that convey fitness may compete with novel selective pressures from anthropogenic noise. Here we show that black-capped chickadees (Poecile atricapillus) use shorter, higher-frequency songs when traffic noise is high, and longer, lower-frequency songs when noise abates. We suggest that chickadees balance opposing selective pressures by use low-frequency songs to preserve vocal characteristics of dominance that repel competitors and attract females, and high frequency songs to increase song transmission when their environment is noisy. The remarkable vocal flexibility exhibited by chickadees may be one reason that they thrive in urban environments, and such flexibility may also support subsequent genetic adaptation to an increasingly urbanized world

Engineered Corynebacterium glutamicum as an endotoxin-free platform strain for lactate-based polyester production

The first biosynthetic system for lactate (LA)-based polyesters was previously created in recombinant Escherichia coli (Taguchi et al. 2008). Here, we have begun efforts to upgrade the prototype polymer production system to a practical stage by using metabolically engineered Gram-positive bacterium Corynebacterium glutamicum as an endotoxin-free platform. We designed metabolic pathways in C. glutamicum to generate monomer substrates, lactyl-CoA (LA-CoA), and 3-hydroxybutyryl-CoA (3HB-CoA), for the copolymerization catalyzed by the LA-polymerizing enzyme (LPE). LA-CoA was synthesized by D-lactate dehydrogenase and propionyl-CoA transferase, while 3HB-CoA was supplied by β-ketothiolase (PhaA) and NADPH-dependent acetoacetyl-CoA reductase (PhaB). The functional expression of these enzymes led to a production of P(LA-co-3HB) with high LA fractions (96.8 mol%). The omission of PhaA and PhaB from this pathway led to a further increase in LA fraction up to 99.3 mol%. The newly engineered C. glutamicum potentially serves as a food-grade and biomedically applicable platform for the production of poly(lactic acid)-like polyester

Elucidation of Beta-Oxidation Pathways in Ralstonia Eutropha H16 by Examination of Global Gene Expression

Ralstonia eutropha H16 is capable of growth and polyhydroxyalkanoate production on plant oils and fatty acids. However, little is known about the triacylglycerol and fatty acid degradation pathways of this bacterium. We compare whole-cell gene expression levels of R. eutropha H16 during growth and polyhydroxyalkanoate production on trioleate and fructose. Trioleate is a triacylglycerol that serves as a model for plant oils. Among the genes of note, two potential fatty acid β-oxidation operons and two putative lipase genes were shown to be upregulated in trioleate cultures. The genes of the glyoxylate bypass also exhibit increased expression during growth on trioleate. We observed that single β-oxidation operon deletion mutants of R. eutropha could grow using palm oil or crude palm kernel oil as the sole carbon source, regardless of which operon was present in the genome, but a double mutant was unable to grow under these conditions. A lipase deletion mutant did not exhibit a growth defect in emulsified oil cultures but did exhibit a phenotype in cultures containing nonemulsified oil. Mutants of the glyoxylate shunt gene for isocitrate lyase were able to grow in the presence of oils, while a malate synthase (aceB) deletion mutant grew more slowly than wild type. Gene expression under polyhydroxyalkanoate storage conditions was also examined. Many findings of this analysis confirm results from previous studies by our group and others. This work represents the first examination of global gene expression involving triacylglycerol and fatty acid catabolism genes in R. eutropha.Malaysia-MIT Biotechnology Partnership Programm