Abstract
BackgroundIntegration of first- and second-generation ethanol processes is one among the alternate approaches that efficiently address the current socio-economic issues of the bioethanol sector. Edible filamentous fungus capable of utilizing pentoses from lignocelluloses and also possessing biomass application as potential animal feed component was used as the fermentation strain for the integration model. This study presents various fermentation aspects of using edible filamentous fungi in the integrated first and second generation ethanol process model.ResultsFermentation of edible strain of N. intermedia on the integrated first and second-generation ethanol substrate (the mixture of dilute acid pretreated and enzymatically hydrolyzed wheat straw and thin stillage from the first-generation ethanol process), showed an ethanol yield maximum of 0.23 ± 0.05 g/g dry substrate. The growth of fungal pellets in presence of fermentation inhibitors (such as acetic acid, HMF and furfural) resulted in about 11 to 45% increase in ethanol production as compared to filamentous forms, at similar growth conditions in the liquid straw hydrolysate. Fungal cultivations in the airlift reactor showed strong correlation with media viscosity, reaching a maximum of 209.8 ± 3.7 cP and resulting in 18.2 ± 1.3 g/L biomass during the growth phase of fungal pellets.ConclusionN. intermedia fermentation showed high sensitivity to the dilute acid lignocellulose pretreatment process, with improved fermentation performance at milder acidic concentrations. The rheological examinations showed media viscosity to be the most critical factor influencing the oxygen transfer rate during the N. intermedia fermentation process. Mycelial pellet morphology showed better fermentation efficiency and high tolerance towards fermentation inhibitors.
Highlights
Integration of first- and second-generation ethanol processes is one among the alternate approaches that efficiently address the current socio-economic issues of the bioethanol sector
It should be considered that the use of genetically modified pentose consumers can create socio-regulatory issues as well as it affects the quality of the animal feed product, DDGS that contributes to a major share of the economics at the 1G-ethanol facility [11]
N. intermedia in the integrated ethanol process Effect of lignocellulose pretreatment on fermentation In order to facilitate the integrated model of first and second-generation ethanol processes, a specially designed fermentation media composed of dilute acid pretreated wheat straw hydrolysate and thin stillage, was used for the filamentous fungal cultivations (Section “Neurospora intermedia fermentation for the integration process”)
Summary
Integration of first- and second-generation ethanol processes is one among the alternate approaches that efficiently address the current socio-economic issues of the bioethanol sector. This study presents various fermentation aspects of using edible filamentous fungi in the integrated first and second generation ethanol process model. It should be considered that the use of genetically modified pentose consumers can create socio-regulatory issues as well as it affects the quality of the animal feed product, DDGS (distiller’s dried grains with solubles) that contributes to a major share of the economics at the 1G-ethanol facility [11]. Finding the right microorganism for ethanol fermentation, capable of consuming pentose sugars and simultaneously maintaining the quality of DDGS narrows the options down to using the edible strains of filamentous fungi as the fermentation microbe [2]
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