Fermentative Conversion of Two-Step Pre-Treated Lignocellulosic Biomass to Hydrogen

Karolina Kucharska,Marian Kamiński,Hubert Cieśliński,Katarzyna Wychodnik,Rafał Łukajtis,Edyta Słupek,Piotr Rybarczyk

doi:10.3390/catal9100858

Abstract

Fermentative hydrogen production via dark fermentation with the application of lignocellulosic biomass requires a multistep pre-treatment procedure, due to the complexed structure of the raw material. Hence, the comparison of the hydrogen productivity potential of different lignocellulosic materials (LCMs) in relation to the lignocellulosic biomass composition is often considered as an interesting field of research. In this study, several types of biomass, representing woods, cereals and grass were processed by means of mechanical pre-treatment and alkaline and enzymatic hydrolysis. Hydrolysates were used in fermentative hydrogen production via dark fermentation process with Enterobacter aerogenes (model organism). The differences in the hydrogen productivity regarding different materials hydrolysates were analyzed using chemometric methods with respect to a wide dataset collected throughout this study. Hydrogen formation, as expected, was positively correlated with glucose concentration and total reducing sugars amount (YTRS) in enzymatic hydrolysates of LCMs, and negatively correlated with concentrations of enzymatic inhibitors i.e., HMF, furfural and total phenolic compounds in alkaline-hydrolysates LCMs, respectively. Interestingly, high hydrogen productivity was positively correlated with lignin content in raw LCMs and smaller mass loss of LCM after pre-treatment step. Besides results of chemometric analysis, the presented data analysis seems to confirm that the structure and chemical composition of lignin and hemicellulose present in the lignocellulosic material is more important to design the process of its bioconversion than the proportion between the cellulose, hemicellulose and lignin content in this material. For analyzed LCMs we found remarkable higher potential of hydrogen production via bioconversion process of woods i.e., beech (24.01 mL H2/g biomass), energetic poplar (23.41 mL H2/g biomass) or energetic willow (25.44 mL H2/g biomass) than for cereals i.e., triticale (17.82 mL H2/g biomass) and corn (14.37 mL H2/g biomass) or for meadow grass (7.22 mL H2/g biomass).

Highlights

The depletion of fossil fuel resources and the accompanying extraction and processing of environmental degradation force the search for alternative technologies for energy production fromCatalysts 2019, 9, 858; doi:10.3390/catal9100858 www.mdpi.com/journal/catalystsCatalysts 2019, 9, 858 biomass resources [1]
lignocellulosic materials (LCMs) of different origin are diversified from the perspective of structural building components, i.e., lignin, hemicellulose and cellulose [31,32,33]
This is because comparison of the hydrogen productivity potential of different lignocellulosic materials in relation to the lignocellulosic biomass composition and the nature of the method used for their bioconversion is an interesting and valuable field of research

Summary

Introduction

The depletion of fossil fuel resources and the accompanying extraction and processing of environmental degradation force the search for alternative technologies for energy production fromCatalysts 2019, 9, 858; doi:10.3390/catal9100858 www.mdpi.com/journal/catalystsCatalysts 2019, 9, 858 biomass resources [1]. One of the alternative energy carriers, which can be produced from non-food raw materials, is hydrogen. The gas with a high hydrogen content obtained from biomass could be used as a raw material for the production of jet, gasoline and diesel fuels [2,3,4]. An alternative is to obtain hydrogen from biomass using biotechnological methods that use the natural possibilities of microorganisms that produce hydrogen as one of the products of metabolic transformation. The raw materials for dark fermentation may be simple sugars and cellulose or starch hydrolyzed into simple sugars [6,8]. It would be desirable to use this process for the production of second generation hydrogen from starch and cellulose-rich waste from the agriculture, food, wood and paper industries [9,10]

Methods

Results

Conclusion