This critical review provides a survey illustrated by recent references of different strategies to achieve a sustainable conversion of biomass to bioproducts. Because of the huge number of chemical products that can be potentially manufactured, a selection of starting materials and targeted chemicals has been done. Also, thermochemical conversion processes such as biomass pyrolysis or gasification as well as the synthesis of biofuels were not considered. The synthesis of chemicals by conversion of platform molecules obtained by depolymerisation and fermentation of biopolymers is presently the most widely envisioned approach. Successful catalytic conversion of these building blocks into intermediates, specialties and fine chemicals will be examined. However, the platform molecule value chain is in competition with well-optimised, cost-effective synthesis routes from fossil resources to produce chemicals that have already a market. The literature covering alternative value chains whereby biopolymers are converted in one or few steps to functional materials will be analysed. This approach which does not require the use of isolated, pure chemicals is well adapted to produce high tonnage products, such as paper additives, paints, resins, foams, surfactants, lubricants, and plasticisers. Another objective of the review was to examine critically the green character of conversion processes because using renewables as raw materials does not exempt from abiding by green chemistry principles (368 references).

Conversion of biomass to selected chemical products

Conversion of Biomass into Chemicals over Metal Catalysts

Green and sustainable manufacture of chemicals from biomass: state of the art

Nucleic acid aptamers, often termed 'chemical antibodies', are functionally comparable to traditional antibodies, but offer several advantages, including their relatively small physical size, flexible structure, quick chemical production, versatile chemical modification, high stability and lack of immunogenicity. In addition, many aptamers are internalized upon binding to cellular receptors, making them useful targeted delivery agents for small interfering RNAs (siRNAs), microRNAs and conventional drugs. However, several crucial factors have delayed the clinical translation of therapeutic aptamers, such as their inherent physicochemical characteristics and lack of safety data. This Review discusses these challenges, highlighting recent clinical developments and technological advances that have revived the impetus for this promising class of therapeutics.

Aptamers as targeted therapeutics: current potential and challenges

A review on the application of inorganic nano-structured materials in the modification of textiles: focus on anti-microbial properties

Sonocatalytic degradation of methylene blue with tio2 pellets in water

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.

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

Bioprocessing of bio-based chemicals produced from lignocellulosic feedstocks

The filamentous fungus T. reesei effectively degrades cellulose and is known to produce various cellulolytic enzymes such as β-glucosidase, endoglucanase, and cellobiohydrolase. The expression levels of each cellulase are controlled simultaneously, and their ratios and synergetic effects are important for effective cellulose degradation. However, in recombinant Saccharomyces cerevisiae, it is difficult to simultaneously control many different enzymes. To construct engineered yeast with efficient cellulose degradation, we developed a simple method to optimize cellulase expression levels, named cocktail δ-integration. In cocktail δ-integration, several kinds of cellulase expression cassettes are integrated into yeast chromosomes simultaneously in one step, and strains with high cellulolytic activity (i.e., expressing an optimum ratio of cellulases) are easily obtained. Although the total integrated gene copy numbers of cocktail δ-integrant strain was about half that of a conventional δ-integrant strain, the phosphoric acid swollen cellulose (PASC) degradation activity (64.9 mU/g-wet cell) was higher than that of a conventional strain (57.6 mU/g-wet cell). This suggests that optimization of the cellulase expression ratio improves PASC degradation activity more so than overexpression. To our knowledge, this is the first report on the expression of cellulase genes by δ-integration and optimization of various foreign genes by δ-integration in yeast. This method should be very effective and easily applied for other multi-enzymatic systems using recombinant yeast.

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Chiaki Ogino

Papers

Sonocatalytic degradation of methylene blue with tio2 pellets in water

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

Bioprocessing of bio-based chemicals produced from lignocellulosic feedstocks

Cocktail δ-integration: a novel method to construct cellulolytic enzyme expression ratio-optimized yeast strains

Genetic engineering to enhance the Ehrlich pathway and alter carbon flux for increased isobutanol production from glucose by Saccharomyces cerevisiae.