Catalysis is at the core of almost every established and emerging chemical process and also plays a central role in the quest for novel technologies for the sustainable production and conversion of energy. Particularly since the early 2000s, a great surge of interest exists in the design and application of micro- and nanometer-sized materials with hollow interiors as solid catalysts. This review provides an updated and critical survey of the ever-expanding material architectures and applications of hollow structures in all branches of catalysis, including bio-, electro-, and photocatalysis. First, the main synthesis strategies toward hollow materials are succinctly summarized, with emphasis on the (regioselective) incorporation of various types of catalytic functionalities within their different subunits. The principles underlying the scientific and technological interest in hollow materials as solid catalysts, or catalyst carriers, are then comprehensively reviewed. Aspects covered include the stabilizat...

Hollow Nano- and Microstructures as Catalysts

Lactic acid was discovered in 1780 by C.W. Scheele in sour milk, and in 1881 Fermi obtained lactic acid by fermentation, resulting in its industrial production. The yearly world lactic acid production is expected to reach 259,000 metric tons by the year 2012. The interest in lactic acid is related to many aspects, among which is its relatively high added-value. In addition, such a chemical is GRAS (Generally Recognized As Safe), being recognized as harmless by the United States Food and Drug Administration, has a market with great growth potential, can be alternatively produced by fermentation or chemical synthesis and can employ a large variety of different waste materials as substrates. Lactic acid has many applications. Its existence in the form of two stereoisomers does in fact make the application of one of them or of the racemic mixture of great concern in different fields. In particular, the food and pharmaceutical industries have a preference for the isomer l (+), the only one that can be metabolized by the human body; however, the chemical industry requires one of the pure isomers or a mixture of both, according to the application. This review describes biotechnological processes to obtain lactic acid from polymeric substrates such as starchy and lignocellulosic materials. Open challenges are related to the technological optimization of the fermentation process and product purification and recovery. In addition, the opportunities and difficulties associated with using raw materials for lactic acid production are discussed.

https://maaz.ihmc.us/rid=1N4KLGGDB-C7FZZY-93H/Castillo%20Martinez%20et%20al.%20-%202013%20-%20Lactic%20acid%20properties,%20applications%20and%20productio.pdf

Lactic acid properties, applications and production: a review.

Lactic acid production from lignocellulose-derived sugars using lactic acid bacteria: Overview and limits

From monomers to polymers from renewable resources: Recent advances

Reaction mechanisms and multi-scale modelling of lignocellulosic biomass pyrolysis

Social and economic development has driven considerable scientific and engineering efforts on the discovery, development and utilization of polymers. Polylactic acid (PLA) is one of the most promising biopolymers as it can be produced from nontoxic renewable feedstock. PLA has emerged as an important polymeric material for biomedical applications on account of its properties such as biocompatibility, biodegradability, mechanical strength and process ability. Lactic acid (LA) can be obtained by fermentation of sugars derived from renewable resources such as corn and sugarcane. PLA is thus an eco-friendly nontoxic polymer with features that permit use in the human body. Although PLA has a wide spectrum of applications, there are certain limitations such as slow degradation rate, hydrophobicity and low impact toughness associated with its use. Blending PLA with other polymers offers convenient options to improve associated properties or to generate novel PLA polymers/blends for target applications. A variety of PLA blends have been explored for various biomedical applications such as drug delivery, implants, sutures and tissue engineering. PLA and their copolymers are becoming widely used in tissue engineering for function restoration of impaired tissues due to their excellent biocompatibility and mechanical properties. The relationship between PLA material properties, manufacturing processes and development of products with desirable characteristics is described in this article. LA production, PLA synthesis and their applications in the biomedical field are also discussed.

https://sfamjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/jam.14290

Polylactic acid: synthesis and biomedical applications.

Development of biocatalysts for production of commodity chemicals from lignocellulosic biomass.

Lignocellulosic biomass is renewable and cheap, and it has the potential to displace fossil fuels for the production of fuels and chemicals. Biomass derived lactic acid is an important compound that can be used as a chemical platform for the production of a variety of important chemicals on a large scale. The quality of the monomers of lactic acid and lactide, as well as the chemical changes induced during polymerization and processing, are crucial parameters for controlling the properties of the resulting polylactic acid (PLA) products. In this review, we outline the process of exploiting biomass for the production of polylactic acid, a biodegradable polymer which is well-known as a sustainable bioplastic material.

/pdf/biomass-to-biodegradable-polymer-pla-3e00mb9hit.pdf

Biomass to biodegradable polymer (PLA)

Lignocellulosic biomass (LCB) is globally available and sustainable feedstock containing sugar-rich platform that can be converted to biofuels and specialty products through appropriate processing. This review focuses on the efforts required for the development of sustainable and economically viable lignocellulosic biorefinery to produce carbon neutral biofuels along with the specialty chemicals. Sustainable biomass processing is a global challenge that requires the fulfillment of fundamental demands concerning economic efficiency, environmental compatibility, and social responsibility. The key technical challenges in continuous biomass supply and the biological routes for its saccharification with high yields of sugar sources have not been addressed in research programs dealing with biomass processing. Though many R&D endeavors have directed towards biomass valorization over several decades, the integrated production of biofuels and chemicals still needs optimization from both technical and economical perspectives. None of the current pretreatment methods has advantages over others since their outcomes depend on the type of feedstock, downstream process configuration, and many other factors. Consolidated bio-processing (CBP) involves the use of single or consortium of microbes to deconstruct biomass without pretreatment. The use of new genetic engineering tools for natively cellulolytic microbes would make the CBP process low cost and ecologically friendly. Issues arising with chemical characteristics and rigidity of the biomass structure can be a setback for its viability for biofuel conversion. Integration of functional genomics and system biology with synthetic biology and metabolic engineering undoubtedly led to generation of efficient microbial systems, albeit with limited commercial potential. These efficient microbial systems with new metabolic routes can be exploited for production of commodity chemicals from all the three components of biomass. This paper provides an overview of the challenges that are faced by the processes converting LCB to commodity chemicals with special reference to biofuels.

Lignocellulosic biomass: Hurdles and challenges in its valorization

Lignocellulosic biomass, of which inedible crops are a renewable source, is expected to become one of the key renewable energy resources in the near future, to deal with global warming and the depletion of conventional fossil fuel resources. It also holds the key to supplying society's basic needs for the sustainable production of chemicals and fuels without impacting the human food supply. Despite this, the production of 2nd generation biofuels and chemicals has not yet been commercialized. Therefore, the challenges involved in the production of lignocellulosic biomass derived fuels and chemicals must be addressed. The search for economic pretreatment methods has been recognized as one of the main hurdles for the processing of biomass to biofuels and chemicals. The conversion of all biomass components, lignin in particular, would greatly contribute to the economic viability of biomass based processes for 2nd generation biofuels and chemicals. The highly organized crystalline structure of cellulose presents an obstacle to its hydrolysis. Hydrolysis of lignocellulose carbohydrates into fermentable sugars requires a number of different biomass degrading enzymes such as cellulases and hemicellulases. Still, a number of technical and scientific issues within pretreatment and hydrolysis remain to be solved. Depending on the raw material and pretreatment technology, the enzyme mixtures must be designed to degrade biomass carbohydrates. Rapid advances in enzyme, microbial and plant engineering would provide the necessary breakthroughs for the successful commercialization of biomass derived fuels and chemicals.

Mamata Singhvi

Papers

Polylactic acid: synthesis and biomedical applications.

Development of biocatalysts for production of commodity chemicals from lignocellulosic biomass.

Biomass to biodegradable polymer (PLA)

Lignocellulosic biomass: Hurdles and challenges in its valorization

Lignocellulose processing: a current challenge