Maize Silage Pretreatment via Steam Refining and Subsequent Enzymatic Hydrolysis for the Production of Fermentable Carbohydrates

Abstract

Maize, also called corn, is one of the most available feedstocks worldwide for lignocellulosic biorefineries. However, a permanent biomass supply over the year is essential for industrial biorefinery application. In that context, ensiling is a well-known agricultural application to produce durable animal feed for the whole year. In this study, ensiled maize was used for steam refining experiments with subsequent enzymatic hydrolysis using the Cellic® CTec2 to test the application possibilities of an ensiled material for the biorefinery purpose of fermentable carbohydrate production. Steam refining was conducted from mild (log R0 = 1.59) to severe conditions (log R0 = 4.12). The yields were determined, and the resulting fractions were characterized. Hereafter, enzymatic hydrolysis of the solid fiber fraction was conducted, and the carbohydrate recovery was calculated. A conversion to monomers of around 50% was found for the mildest pretreatment (log R0 = 1.59). After pretreatment at the highest severity of 4.12, it was possible to achieve a conversion of 100% of the theoretical available carbohydrates. From these results, it is clear that a sufficient pretreatment is necessary to achieve sufficient recovery rates. Thus, it can be concluded that ensiled maize pretreated by steam refining is a suitable and highly available feedstock for lignocellulosic biorefineries. Ultimately, it can be assumed that ensiling is a promising storage method to pave the way for a full-year biomass supply for lignocellulosic biorefinery concepts.

SPAD Leaf Greenness Index: Green Mass Yield Indicator of Maize (Zea mays L.), Genetic and Agriculture Practice Relationship

“…Allocating the field area for maize increases the efficiency of crop rotation, while a higher proportion of maize silage in the ration improves the profitability of animal feeding. Due to the deterioration of milk production profitability, it is necessary to further increase the maize cultivation for silage [ 22 ] and measures aimed at improving the quality of the produced feed [ 23 ]. Therefore, field research on the improvement of maize agrotechnics is a response to the above statement.…”

Analytical Characterization and Inhibitor Detection in Liquid Phases Obtained After Steam Refining of Corn Stover and Maize Silage

“…The high availability of maize and its products are displayed in estimates for the worldwide corn production. Based on data of the Food and Agriculture Organization of the United Nations (FAO) and literature values for the straw/kernel-ratio, Krafft et al (2020b) calculated an estimated annual maize production of 2.15–2.64 billion tons for 2018. Updated FAO data for 2019 show quite similar values ( FAOSTAT, 2020 ).…”

“…In that context ensiling was mentioned in literature as a suitable storage method for biomass in biorefineries ( Oleskowicz-Popiel et al, 2011 ). Moreover, maize silage (MS) has a lower grade of recalcitrance against enzymatic degradation, mainly due to lower lignin contents, but a pretreatment is also necessary to receive sufficient results after enzymatic hydrolysis (EH) ( Krafft et al, 2020b ). In the last years steam refining was conducted for pretreatments of wood ( Schütt et al, 2011 ; Schütt et al, 2012 ), forest residues ( Janzon et al, 2014 ), CS ( Krafft et al, 2020a ), MS ( Krafft et al, 2020b ) or waste medium density fiberboards (MDF) ( Hagel and Saake, 2020 ).…”

“…Moreover, maize silage (MS) has a lower grade of recalcitrance against enzymatic degradation, mainly due to lower lignin contents, but a pretreatment is also necessary to receive sufficient results after enzymatic hydrolysis (EH) ( Krafft et al, 2020b ). In the last years steam refining was conducted for pretreatments of wood ( Schütt et al, 2011 ; Schütt et al, 2012 ), forest residues ( Janzon et al, 2014 ), CS ( Krafft et al, 2020a ), MS ( Krafft et al, 2020b ) or waste medium density fiberboards (MDF) ( Hagel and Saake, 2020 ). Most studies were conducted to enhance the enzymatic digestibility for the production of monomeric carbohydrates, but attempts for MDF fiber recycling after steam refining are reported as well ( Hagel et al, 2021 ).…”

“…Former studies depict yields, characterization and utilization of the fiber fraction after steam refining ( Krafft et al, 2020a ; Krafft et al, 2020b ). In this study, a detailed analytical characterization of filtrates obtained after steam refining of CS ( Krafft et al, 2020a ) and MS ( Krafft et al, 2020b ) will be described to complete a full overview about the obtained fractions. Therefore, results from carbohydrate analysis and molar mass distribution, as well as results on organic acids and furans will be presented.…”