Abstract
The production of a thermostable and highly alkaline pectinase by Bacillus pumilus dcsr1 was optimized in solid-state fermentation (SSF) and the impact of various treatments (chemical, enzymatic, and in combination) on the quality of ramie fibres was investigated. Maximum enzyme titer (348.0 ± 11.8 Ug−1 DBB) in SSF was attained, when a mixture of agro-residues (sesame oilseed cake, wheat bran, and citrus pectin, 1 : 1 : 0.01) was moistened with mineral salt solution (a w 0.92, pH 9.0) at a substrate-to-moistening agent ratio of 1 : 2.5 and inoculated with 25% of 24 h old inoculum, in 144 h at 40°C. Parametric optimization in SSF resulted in 1.7-fold enhancement in the enzyme production as compared to that recorded in unoptimized conditions. A 14.2-fold higher enzyme production was attained in SSF as compared to that in submerged fermentation (SmF). The treatment with the enzyme significantly improved tensile strength and Young's modulus, reduction in brittleness, redness and yellowness, and increase in the strength and brightness of ramie fibres.
Highlights
Solid-state fermentation (SSF) takes place in absence or near absence of free flowing water [1] and is of special economic interest for countries having abundant biomass and agroindustrial residues
Efforts have been made to exploit filamentous fungi in SSF for the production of various products, and further attempts are being made to explore the possibility of using bacterial strains in SSF systems [1, 30]
The direct observation of the microbe in solid substrate remains a difficulty in all studies
Summary
Solid-state fermentation (SSF) takes place in absence or near absence of free flowing water [1] and is of special economic interest for countries having abundant biomass and agroindustrial residues. Development of high brittleness is a major disadvantage of the fibre for the application in textile industry [25], and the condition is caused by the nonspecific treatment with chemicals or with crude enzyme preparations having. In this investigation an attempt has been made to optimize various physical and chemical parameters to produce elevated levels of thermo-alkali stable pectinase using agriculture residues in SSF by the alkali tolerant Bacillus pumilus dcsr (GenBank accession AY426610). Thecost effective production of this valuable enzyme for the processing of ramie fibres [15] will enhance its applicability in the development of green technology. The effect of various treatments on the physical properties of ramie fibre is discussed
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