Abstract
BackgroundDevelopment of efficient methods for production of renewable fuels from lignocellulosic biomass is necessary to maximize yields and reduce operating costs. One of the main challenges to industrial application of the lignocellulosic conversion process is the high costs of cellulolytic enzymes. Recycling of enzymes may present a potential solution to alleviate this problem. In the present study enzymes associated with the insoluble fraction were recycled after enzymatic hydrolysis of pretreated sugarcane bagasse, utilizing different processing conditions, enzyme loadings, and solid loadings.ResultsIt was found that the enzyme blend from Chrysoporthe cubensis and Penicillium pinophilum was efficient for enzymatic hydrolysis and that a significant portion of enzyme activity could be recovered upon recycling of the insoluble fraction. Enzyme productivity values (g glucose/mg enzyme protein) over all recycle periods were 2.4 and 3.7 for application of 15 and 30 FPU/g of glucan, representing an increase in excess of ten times that obtained in a batch process with the same enzyme blend and an even greater increase compared to commercial cellulase enzymes.ConclusionsContrary to what may be expected, increasing lignin concentrations throughout the recycle period did not negatively influence hydrolysis efficiency, but conversion efficiencies continuously improved. Recycling of the entire insoluble solids fraction was sufficient for recycling of adhered enzymes together with biomass, indicative of an effective method to increase enzyme productivity.
Highlights
Development of efficient methods for production of renewable fuels from lignocellulosic biomass is necessary to maximize yields and reduce operating costs
Characterization of the biomass and enzyme blend Sugarcane bagasse was utilized as a model substrate for the saccharification experiments due to its availability as a potential lignocellulosic feedstock in Brazil
The bagasse was submitted to thermochemical pretreatment with 1.5% NaOH at 120°C for one hour after which approximately 50% of the lignin was removed (Table 1), facilitating enzyme attack of the cellulose and hemicellulose fractions
Summary
Development of efficient methods for production of renewable fuels from lignocellulosic biomass is necessary to maximize yields and reduce operating costs. One of the main challenges to industrial application of the lignocellulosic conversion process is the high costs of cellulolytic enzymes. The production of bioethanol from lignocellulosic biomass is a subject of great interest because cellulosic ethanol presents the potential to substitute gasoline, promote rural development, and reduce greenhouse gases, while utilizing material not fit for human consumption [1]. The major bottleneck of enzyme-catalyzed hydrolysis is the high cost of enzymes and relatively low yields. Blending crude enzyme extracts from different fungi has received less attention than blending specific enzymes, but it shows great potential since no activities are lost in concentration/purification processes, and a wide spectrum of enzyme activities is maintained. Synergy among enzymes from individual enzyme extracts is another advantage to utilization of these enzyme blends [7,8]
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