There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

In pursuit of more sustainable and competitive biorefineries, the effective valorisation of lignin is key. An alluring opportunity is the exploitation of lignin as a resource for chemicals. Three technological biorefinery aspects will determine the realisation of a successful lignin-to-chemicals valorisation chain, namely (i) lignocellulose fractionation, (ii) lignin depolymerisation, and (iii) upgrading towards targeted chemicals. This review provides a summary and perspective of the extensive research that has been devoted to each of these three interconnected biorefinery aspects, ranging from industrially well-established techniques to the latest cutting edge innovations. To navigate the reader through the overwhelming collection of literature on each topic, distinct strategies/topics were delineated and summarised in comprehensive overview figures. Upon closer inspection, conceptual principles arise that rationalise the success of certain methodologies, and more importantly, can guide future research to further expand the portfolio of promising technologies. When targeting chemicals, a key objective during the fractionation and depolymerisation stage is to minimise lignin condensation (i.e. formation of resistive carbon–carbon linkages). During fractionation, this can be achieved by either (i) preserving the (native) lignin structure or (ii) by tolerating depolymerisation of the lignin polymer but preventing condensation through chemical quenching or physical removal of reactive intermediates. The latter strategy is also commonly applied in the lignin depolymerisation stage, while an alternative approach is to augment the relative rate of depolymerisation vs. condensation by enhancing the reactivity of the lignin structure towards depolymerisation. Finally, because depolymerised lignins often consist of a complex mixture of various compounds, upgrading of the raw product mixture through convergent transformations embodies a promising approach to decrease the complexity. This particular upgrading approach is termed funneling, and includes both chemocatalytic and biological strategies.

/pdf/chemicals-from-lignin-an-interplay-of-lignocellulose-1th1dk0l26.pdf

Chemicals from lignin: an interplay of lignocellulose fractionation, depolymerisation, and upgrading

Bioethanol production from agricultural wastes: An overview

Trends in bioconversion of lignocellulose: Biofuels, platform chemicals & biorefinery concept

Overcoming the recalcitrance (resistance of plant cell walls to deconstruction) of lignocellulosic biomass is a key step in the production of fuels and chemicals. The recalcitrance is due to the highly crystalline structure of cellulose which is embedded in a matrix of polymers-lignin and hemicellulose. The main goal of pretreatment is to overcome this recalcitrance, to separate the cellulose from the matrix polymers, and to make it more accessible for enzymatic hydrolysis. Reports have shown that pretreatment can improve sugar yields to higher than 90% theoretical yield for biomass such as wood, grasses, and corn. This paper reviews different leading pretreatment technologies along with their latest developments and highlights their advantages and disadvantages with respect to subsequent hydrolysis and fermentation. The effects of different technologies on the components of biomass (cellulose, hemicellulose, and lignin) are also reviewed with a focus on how the treatment greatly enhances enzymatic cellulose digestibility.

/pdf/chemical-and-physicochemical-pretreatment-of-lignocellulosic-4eshdcsnor.pdf

Chemical and physicochemical pretreatment of lignocellulosic biomass: a review.

Liquid hot water pretreatment of lignocellulosic biomass for bioethanol production accompanying with high valuable products.

http://ir.giec.ac.cn/bitstream/344007/8493/2/Two-step%20liquid%20hot%20water%20pretreatment%20of%20Eucalyptus%20grandis%20to%20enhance%20sugar%20recovery%20and%20enzymatic%20digestibility%20of%20cellulose.pdf

Two-step liquid hot water pretreatment of Eucalyptus grandis to enhance sugar recovery and enzymatic digestibility of cellulose.

https://www.tpbin.com/Uploads/Subjects/af12c540-35b0-4328-856d-0571b28f9116.pdf

Liquid hot water pretreatment of sugarcane bagasse and its comparison with chemical pretreatment methods for the sugar recovery and structural changes.

http://ir.giec.ac.cn/bitstream/344007/10178/1/High%20consistency%20enzymatic%20saccharification%20of%20sweet%20sorghum%20bagasse%20pretreated%20with%20liquid%20hot%20water.pdf

Qiang Yu

Papers

Liquid hot water pretreatment of lignocellulosic biomass for bioethanol production accompanying with high valuable products.

Two-step liquid hot water pretreatment of Eucalyptus grandis to enhance sugar recovery and enzymatic digestibility of cellulose.

Liquid hot water pretreatment of sugarcane bagasse and its comparison with chemical pretreatment methods for the sugar recovery and structural changes.

High consistency enzymatic saccharification of sweet sorghum bagasse pretreated with liquid hot water.

Effects of different pretreatment methods on chemical composition of sugarcane bagasse and enzymatic hydrolysis.