Correction to: Characterization of a glucose tolerant ß-glucosidase from Aspergillus unguis with high potential as a blend-in for biomass hydrolyzing enzyme cocktails.

In the original publication of the article, the affiliation of two co-authors Prajeesh Kooloth-Valappil and Meera Christopher was published incompletely. The correct affiliation of the authors should read " Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, India".

Characterization of a glucose tolerant ß-glucosidase from Aspergillus unguis with high potential as a blend-in for biomass hydrolyzing enzyme cocktails.

OBJECTIVES: Characterization of glucose tolerant beta glucosidase (GT-BGL) secreted by Aspergillus unguis NII 08123, determination of the gene and protein sequences of the enzyme and establishing its performance in blends for lignocellulose hydrolysis. RESULTS: Supplementation of A. unguis beta glucosidase (BGL) to cellulase released 1.6 times more sugar within 12 h during the hydrolysis of lignocellulosic biomass. The enzyme was determined to be similar to BGL-F from Emericella nidulans by MALDI-TOF analysis, and was found to be a GH3 family protein. Molecular Docking simulation studies showed that the enzyme has lesser affinity for glucose (- 5.7 kcal/mol) compared to its substrate cellobiose (- 7.5 kcal/mol). The residues present in the N-terminal domain are mostly involved in bond formation with both the substrate and the product, while the C-terminal domain contains the catalytic region. In-silico studies showed that its predicted structure is unlike that of previously reported BGLs, which might provide a clue to its exceptional catalytic activity. CONCLUSION: The GT-BGL from A. unguis NII 08123 was proven effective as a blend in for biomass hydrolyzing enzyme cocktails and the possible reasons for its glucose tolerance was determined through studies on its modeled structure.

Highly glucose tolerant ß-glucosidase from Aspergillus unguis: NII 08123 for enhanced hydrolysis of biomass.

Aspergillus unguis NII-08123, a filamentous fungus isolated from soil, was found to produce ß-glucosidase (BGL) activity with high glucose tolerance. Cultivation of the fungus in different carbon sources resulted in the secretion of different isoforms of the enzyme. A low molecular weight isoform, which retained ~60 % activity in the presence of 1.5 M glucose, was purified to homogeneity and the purified enzyme exhibited a temperature and pH optima of 60 °C and 6, respectively. The K(m) and V(max) of the enzyme were 4.85 mM and 2.95 U/mg, respectively, for 4-nitrophenyl ß-D-glucopyranoside. The glucose inhibition constant of the enzyme was 0.8 M, indicating high glucose tolerance, and this is the second-highest glucose tolerance ever reported from the Aspergillus nidulans group. The glucose-tolerant BGL from A. unguis, when supplemented to cellulase preparation from Penicillium, could improve biomass hydrolysis efficiency by 20 % in 12 h compared to the enzyme without additional beta glucosidase supplementation. The beta glucosidase from A. unguis is proposed as a highly potent "blend-in" for biomass saccharifying enzyme preparations.

Lignocellulosic ethanol in India: Prospects, challenges and feedstock availability.

India has a pressing need for renewable transportation fuels and bio-ethanol is considered as one of the most important options. Currently the country mandates use of 5% ethanol blending in motor gasoline in several states. The ethanol for this is mainly sourced from molasses feedstock, but this is barely sufficient to meet the current demand. Lignocellulosic biomass is the alternative but the availability of this resource is poorly documented. Also the technologies for ethanol production from lignocellulosic biomass are under preliminary stages of development which warrants extensive R&D in this field. The review discusses the current status of molasses based ethanol production in India and its limitations, the state of technologies for second generation ethanol production and the availability of feedstock for bio-ethanol production.