Editorial: chemicals and bioproducts from biomass

© 2016 The Author(s). This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated. The current driving force for the development of “clean” technologies for the production of fuels and chemicals from renewable resources stems mainly from environmental concerns, which have overshadowed concerns regarding the depletion of fossil fuel reserves and the price instability of crude oil. To accommodate the increasing interest in biotechnology for the production of chemicals, Biotechnology for Biofuels (BfB) took the decision to widen its scope to also include articles on the biological production of chemicals and bioproducts derived from biomass and CO2. Whereas a large proportion of the articles in BfB still deal with the pretreatment, hydrolysis and bioconversion of lignocellulosic biomass to ethanol, the journal also has published a number of interesting articles related to bio-based chemicals and other bioproducts. This retrospective thematic issue assembles recent articles since 2015 to highlight these areas of research. An interesting observation when compiling this thematic issue was that of these 32 articles, 11 originated from China—by far the most from any one country. The topics covered by these selected articles are rather diverse, with feedstocks ranging from sugars to syngas (a mixture of CO, H2 and CO2), while the products include various chemicals and potential alternative biofuels such as acetate, n-butanol, 1-propanol, 1,2-propanediol, lipids, shortand medium-chain monocarboxylic acids and their corresponding alcohols, α-linolenic acid, succinic acid, glycolic acid, 3-hydroxypropionic acid, geraniol, chitin, isoprene, alkanes, 1-alkenes and biohythane (a mixture of biomethane and biohydrogen) produced from waste sludge using microbial electrolysis cells. The increasing number of articles dealing with the use of glycerol as feedstock for the production of bioproducts such as malic acid, 1,3-propanediol, 2,3-butanediol, triacylglycerides, erythritol and citric acid is encouraging, since valorisation of the huge amounts of crude glycerol generated as the main by-product of biodiesel production by transesterification of animal fats and plant oils has become imperative. Also included in this collection of articles is a review by Luo et al. [1] on the microbial synthesis of poly-γ-glutamic acid, a bio-based chemical that is already widely used in several industries and the production of which by microbial fermentation is deemed cost-effective. Apart from conventional bioprocesses such as anaerobic digestion and fermentation, a significant increase was noted in the number of articles involving metabolic engineering and also protein engineering aimed at the production of chemicals and alternative biofuels. The genetically tractable Escherichia coli still featured as the favoured host microorganism for metabolic engineering. Yao et al. [2] investigated the co-metabolism of glycerol and glucose to determine the metabolic potential of a genetically engineered E. coli strain as a platform for the production of biofuels and chemicals. For the production of geraniol, an acyclic monoterpene alcohol that finds application in the perfume and other industries, Liu et al. [3] overexpressed several key pathway genes in E. coli. The production of n-butanol, which has excellent qualities for an alternative fuel, was investigated by Saini et al. [4] through engineering of the central metabolism of E. coli. A novel approach to the biosynthesis of longchain 1-alkenes from low-cost triacylglycerols as a “dropin” biofuel is described in the article by Yan et al. [5] on the development of a tandem biotransformation process incorporating cell-free systems (purified enzymes or cellfree extracts) and engineered E. coli whole cells. Protein engineering of key enzymes offers the prospect of tailoring biofuel formulations to desired specifications [6]. This selection of articles includes reports on metabolic engineering also of other microorganisms aimed at a variety of bioproducts. Extensive engineering of the workhorse of industrial biotechnology, Saccharomyces Open Access Biotechnology for Biofuels