Lignocellulose integration to 1G-ethanol process using filamentous fungi: fermentation prospects of edible strain of Neurospora intermedia

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.

Inhibitory and Stimulatory Effects of Fruit Bioactive Compounds on Edible Filamentous Fungi: Potential for Innovative Food Applications

“…N. intermedia has been reported to grow in both filament and pellet forms in previous studies [71,74]. pH was reported to be a significant factor in the pellet formation of N. intermedia, where a pH of 3.5-4 resulted in the formation of pellets with a smooth outer surface [71].…”

A Critical Review on the Ubiquitous Role of Filamentous Fungi in Pollution Mitigation

“…However, it has not been widely explored for submerged cultivation of filamentous fungi. One example includes the work carried out by Nair et al [70] during a research approach for integration of substrates used for production of first-and second-generation ethanol, namely sidestreams from ethanol production from starch and lignocellulosic materials, respectively. The proposed strategy would avoid the supplementation of the cultivation medium with costly nutrients that might also entail an environmental footprint.…”

Ethanol production by a filamentous fungal strain Byssochlamys fulva AM130 under alternating aerobic and oxygen-limited conditions

“…Ethanol yields ranging from 0.18 to 0.46 g/g have been documented for strains of Fusarium oxysporum, one of the best fungal producers of ethanol [21]. Nair et al [18] reported an ethanol yield of 0.23 g/g for Neurospora intermedia in a mixture of dilute acid pretreated and enzymatically hydrolyzed wheat straw and thin stillage from the first-generation ethanol process. A more recent study, targeting direct fermentation of lignocellulosic biomass using a mixed consortium of fungi, has shown ethanol yields of 0.037, 0.40, and 0.41 g/g for the fungi Bjerkandera adusta, Fomitopsis palustris, and Schizophyllum commune, respectively, while using glucose as the carbon source [7].…”

“…The ability to sustain growth and survive under anaerobic conditions, and the tolerance of these fungi to ethanol which they produce under anaerobic conditions have been relatively understudied and so is their potential to directly produce ethanol from lignocellulosic biomass. Recent studies have indicated the potential of using edible filamentous fungi for valorization of spent liquors and C5-rich streams from grain and lignocellulosic biorefineries where edible fungal protein is generated along with ethanol fermentation [17,18]. Apparently, most fungi are capable of utilizing cellulose and hemicellulose-derived sugars, but their ability to synthesize lignocellulolytic enzymes varies.…”