Lignocellulose biorefinery encompasses process engineering and biotechnology tools for the processing of lignocellulosic biomass for the manufacturing of bio-based products (such as biofuels, bio-chemicals, biomaterials). While, lignocellulose biorefinery offers clear value proposition, success at industrial level has not been vibrant for the commercial production of renewable chemicals and fuels. This is because of high capital and operating expenditures, irregularities in biomass supply chain, technical process immaturity, and scale up challenges. As a result, commercial production of biochemicals and biofuels with right economics is still lagging behind. To hit the market place, efforts are underway by bulk and specialty chemicals producing companies like DSM (Succinic acid, Cellulosic ethanol), Dow-DuPont (1,3-Propanediol, 1,4-Butanediol), Clariant-Global bioenergies-INEOS (bio-isobutene), Braskem (Ethylene, polypropylene), Raizen, Gran-bio and POET-DSM (Cellulosic ethanol), Amyris (Farnesene), and several other potential players. This paper entails the concept of lignocellulose biorefinery, technical challenges for industrialization of renewable fuels and bulk chemicals and future directions.

Plants have evolved several adaptive strategies through physiological changes in response to herbivore attacks. Plant secondary metabolites (PSMs) are synthesized to provide defensive functions and regulate defense signaling pathways to safeguard plants against herbivores. Herbivore injury initiates complex reactions which ultimately lead to synthesis and accumulation of PSMs. The biosynthesis of these metabolites is regulated by the interplay of signaling molecules comprising phytohormones. Plant volatile metabolites are released upon herbivore attack and are capable of directly inducing or priming hormonal defense signaling pathways. Secondary metabolites enable plants to quickly detect herbivore attacks and respond in a timely way in a rapidly changing scenario of pest and environment. Several studies have suggested that the potential for adaptation and/or resistance by insect herbivores to secondary metabolites is limited. These metabolites cause direct toxicity to insect pests, stimulate antixenosis mechanisms in plants to insect herbivores, and, by recruiting herbivore natural enemies, indirectly protect the plants. Herbivores adapt to secondary metabolites by the up/down regulation of sensory genes, and sequestration or detoxification of toxic metabolites. PSMs modulate multi-trophic interactions involving host plants, herbivores, natural enemies and pollinators. Although the role of secondary metabolites in plant-pollinator interplay has been little explored, several reports suggest that both plants and pollinators are mutually benefited. Molecular insights into the regulatory proteins and genes involved in the biosynthesis of secondary metabolites will pave the way for the metabolic engineering of biosynthetic pathway intermediates for improving plant tolerance to herbivores. This review throws light on the role of PSMs in modulating multi-trophic interactions, contributing to the knowledge of plant-herbivore interactions to enable their management in an eco-friendly and sustainable manner.

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The emergence of lignocellulosic biorefineries (LBRs) over the past few decades has shown tremendous potential for the development of sustainable renewable resources. Lignocellulosic biorefineries not only meet energy needs but also mitigate environmental problems by replacing conventional petroleum sources. Round the year availability of lignocellulosic biomass (LCB) with affordable price is a major factor in the development of biorefineries. It consists primarily of sugar polymers (cellulose and hemicellulose) and lignin, which can be used to produce second‐generation (2G) biofuels such as bioethanol, biohydrogen, biobutanol, and renewable chemicals like lactic acid, succinic acid, and 5‐hydroxymethylfurfural, the compound annual growth rate (CAGR) of which is predicted to be 16.43% by 2025. Several multinational companies, such as Raizen, Du Pont, BASF AG, Cargill, Braskem, and others have embarked on bio‐based chemicals / biofuels production. However, biochemicals and even biofuels have not achieved the desired commercial goals due to a lack of feasibility and a lack of innovative techniques for bioprocessing or genetic engineering. Inappropriate feedstock logistics and lack of accurate life‐cycle analyses of processes / products were also major drawbacks in developing commercially viable technologies from LCB. In this paper, therefore, recent technological advancements in LBRs, the current bio‐renewable commercialization situation, and the intrinsic role of biorefinery in the circular bioeconomy have been elucidated. © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd

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