Pretreatment of lignocellulosic material with fungi capable of higher lignin degradation and lower carbohydrate degradation improves substrate acid hydrolysis and the eventual conversion to ethanol

Authors: Kuhar, Sarika; Nair, Lavanya M.; Kuhad, Ramesh C.

Source: Canadian Journal of Microbiology, Volume 54, Number 4, April 2008 , pp. 305-313(9)

Publisher: NRC Research Press

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Abstract:

Phanerochaete chrysosporium, Pycnoporus cinnabarinus,and fungal isolates RCK-1 and RCK-3 were tested for their lignin degradation abilities when grown on wheat straw (WS) and Prosopis juliflora (PJ) under solid-state cultivation conditions. Fungal isolate RCK-1 degraded more lignin in WS (12.26% and 22.64%) and PJ (19.30% and 21.97%) and less holocellulose in WS (6.27% and 9.39%) and PJ (3.01% and 4.58%) after 10 and 20 days, respectively, than other fungi tested. Phanerochaete chrysosporium caused higher substrate mass loss and degraded more of holocellulosic content (WS: 55.67%; PJ: 48.89%) than lignin (WS: 18.89%; PJ: 20.20%) after 20 days. The fungal pretreatment of WS and PJ with a high-lignin-degrading and low-holocellulose-degrading fungus (fungal isolate RCK-1) for 10 days resulted in (i) reduction in acid load for hydrolysis of structural polysaccharides (from 3.5% to 2.5% in WS and from 4.5% to 2.5% in PJ), (ii) an increase in the release of fermentable sugars (from 30.27 to 40.82 g·L-1 in WS and from 18.18 to 26.00 g·L-1 in PJ), and (iii) a reduction in fermentation inhibitors (total phenolics) in acid hydrolysate of WS (from 1.31 to 0.63 g·L-1) and PJ (from 2.05 to 0.80 g·L-1). Ethanol yield and volumetric productivity from RCK-1-treated WS (0.48 g·g-1 and 0.54 g·L-1·h-1, respectively) and PJ (0.46 g·g-1 and 0.33 g·L-1·h-1, respectively) were higher than untreated WS (0.36 g·g-1 and 0.30 g·L-1·h-1, respectively) and untreated PJ (0.42 g·g-1 and 0.21 g·L-1·h-1, respectively).

Les capacités de dégradation de la lignine par Phanerochaete chrysosporium, Pycnoporus cinnabarinus et par les isolats fongiques RCK-1 et RCK-3 cultivés sur des paillis de paille de blé (PB) ou de Prosopis juliflora (PJ) ont été testées. L’isolat RCK-1 dégradait plus de lignine sur PB (12,26 % et 22,64 %) et sur PJ (19,30 % et 21,97 %) et moins de holocellulose sur PB (6,27 % et 9,39 %) et sur PJ (3,01 % et 4,58 %) après 10 et 20 jours, respectivement, comparativement aux autres champignons testés, alors que Phanerochaete chrysosporium causait une plus grande perte de poids de substrat et dégradait plus de holocellulose (PB : 55,67 %; PJ : 48,89 %) que de lignine (PB : 18,89 % ; PJ : 20,20 %) après 20 jours. Le prétraitement fongique de la PB et de PJ pendant 10 jours avec le champignon dégradant le plus de lignine et le moins de holocellulose (l’isolat fongique RCK-1) a résulté en (i) une réduction de la charge acide pour l’hydrolyse des polysaccharides de structure (de 3,5 % à 2,5 % sur PB et de 4,5 % à 2,5 % sur PJ), (ii) une augmentation de la libération de sucres fermentables (de 30,27 à 40,82 g·L-1 sur PB et de 18,18 à 26,00 g·L-1 sur PJ) et (iii) une réduction de la quantité d’inhibiteurs de la fermentation (phénols totaux) dans l’hydrolysat acide de PB (de 1,31 à 0,63 g·L-1) et de PJ (2,05 à 0,80 g·L-1). Le rendement en éthanol et la productivité volumétrique de la PB (0,48 g·g-1 et 0,54 g·L-1·h-1, respectivement) et de PJ (0,46 g·g-1 et 0,33 g·L-1·h-1, respectivement) traités avec l’isolat RCK-1 étaient supérieurs à ceux de la PB (0,36 g·g -1 et 0,30 g·L-1·h-1, respectivement) et de PJ (0,42 g·g-1 et 0,21 g·L-1·h-1, respectivement) non traités.

Document Type: Research Article

Publication date: April 1, 2008

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  • Published since 1954, this monthly journal contains new research in the field of microbiology including applied microbiology and biotechnology; microbial structure and function; fungi and other eucaryotic protists; infection and immunity; microbial ecology; physiology, metabolism and enzymology; and virology, genetics, and molecular biology. It also publishes review articles and notes on an occasional basis, contributed by recognized scientists worldwide.
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