Ethanol production from spent mushroom substrate
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Date
2014
Authors
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Publisher
CCSHAU
Abstract
The use of spent mushroom substrate for ethanol production provides an alternative opportunity for more
sustainable development of renewable resources. Mushroom industry is considered problematic due to disposal of
spent substrate left after mushroom production as waste. The spent substrate has great potential for conversion into
sugar by partial degradation of agro-residues that allows yeast growth for conversion of glucose to ethanol by
using three main steps: pretreatment, hydrolysis and fermentation. Pretreatment must be cost-effective besides
improving the formation of sugars by hydrolysis. Alkali (Sodium hydroxide) pretreatment of lignocellulosic
materials reduce the crystallinity of cellulose and increase the porosity of the lignocellulosic materials. Pretreated
biomass can be fermented by separate hydrolysis and fermentation. In separate hydrolysis and fermentation (SHF),
the hydrolysate can be fermented to ethanol in a sequential process where the hydrolysis of cellulose and the
fermentation is carried out in different units. Sugars produced as a result of hydrolysis under optimum conditions
are fermented to ethanol by yeast. For the present study, Spent mushroom substrate (SMS) after the harvest of
oyster and button mushroom obtained from mushroom production technology lab, Department of Plant Pathology
CCSHAU, Hisar was ground to different mesh size (0.5, 1.0, 1.5 and 2.0 mm). Spent oyster mushroom substrate
contained 36.19% cellulose, 22.24% hemicellulose and 11.99% lignin while spent button mushroom substrate
contained 17.60% cellulose, 18.23% hemicellulose and 10.70% lignin before pretreatment. Spent oyster mushroom
substrate due to its higher cellulose content was used for ethanol production. Pretreatment of spent oyster
mushroom substrate of different particle size (0.5-2 mm) was carried out using different sodium hydroxide conc.
(0.5-2%) at 1:10 (w/v) at 15 psi for 1 h. Pretreatment of 1mm mesh size spent mushroom substrate with 2%
sodium hydroxide at 15 psi for 1 h resulted in 59% delignification. The optimum concentration of cellulase
enzyme and hydrolysis temperature of SMS was found to be 0.20 FPU/g substrate at 50˚C that resulted in about
70.11% sugar release after 2 h shaking.Fermentation of hydrolyzed spent mushroom substrate supplemented with
0.3% urea, with the culture of Saccharomyces cerevisiae inoculated @0.5% (w/v) resulted in production of 2.7 and
3.5% ethanol after 72 h fermentation at 30 and 35˚C respectively. The fermented residue was found to contain
about 4.3% cellulose but 19.2% crude protein. Efforts in process integration and optimization will help to improve
the economy of the process.
MAJOR ADVISOR DEGREE HOLDER
Description
Keywords
Ethanol, Pretreatment, Separate hydrolysis and fermentation, Spent mushroom substrate