Enhanced hydrolysis of lignocellulosic biomass with doping of a highly thermostable recombinant laccase

A highly thermostable laccase from Geobacillus sp. strain WSUCF1 was cloned into Escherichia coli (E. coli) using pRham N-His SUMO expression system. The thermostable laccase with a molecular weight ~30 kDa had a t_1/2 (pH 6.0) of 120 h at 50 °C. The homology modelling for laccase structure showed the presence of Cu active centers with His and Cys residues involved in the active site and ligand binding activity of the enzyme, respectively. The K_m, V_max, K_cat and K_cat/K_m values of the purified enzyme with ABTS were found to be 0.146 mM, 1.52 U/mg, 1037 s^-1 and 7102.7 s^-1 mM^-1, respectively. The doping of recombinant WSUCF1 laccase to commercial enzyme cocktails Accellerase® 1500 and Cellic CTec2 improved the hydrolysis of untreated, alkali and acid treated corn stover by 1.31-2.28 times and bagasse by 1.32-2.02 times. Further, in-house enzyme cocktails with laccase hydrolyzed untreated, alkali and acid treated bagasse and gave 1.44, 1.1, and 0.92 folds higher sugar, respectively, when compared with Accellerase 1500. The results suggested that thermostable laccase can aid in the improved hydrolysis of lignocellulosic biomass.

Thermostable xylanases from thermophilic fungi and bacteria: Current perspective

Thermostable xylanases from thermophilic fungi and bacteria have a wide commercial acceptability in feed, food, paper and pulp and bioconversion of lignocellulosics with an estimated annual market of USD 500 Million. The genome wide analysis of thermophilic fungi clearly shows the presence of elaborate genetic information coding for multiple xylanases primarily coding for GH10, GH11 in addition to GH7 and GH30 xylanases. The transcriptomics and proteome profiling has given insight into the differential expression of these xylanases in some of the thermophilic fungi. Bioprospecting has resulted in identification of novel thermophilic xylanases that have been endorsed by the industrial houses for heterologous over- expression and formulations. The future use of xylanases is expected to increase exponentially for their role in biorefineries. The discovery of new and improvement of existing xylanases using molecular tools such as directed evolution is expected to be the mainstay to meet increasing demand of thermostable xylanases.

Evaluating novel fungal secretomes for efficient saccharification and fermentation of composite sugars derived from hydrolysate and molasses into ethanol

This paper evaluates the ability of secretome from two thermotolerant fungal strains (Aspergillus terreus 9DR and Achaetomium strumarium 10DR) for boosting the hydrolytic efficiency of benchmark cellulolytic preparation (Cellic CTec2). Further we report enhanced saccharification of different agro-residues under semi-aerobic when compared to aerobic conditions. The mass spectroscopic analysis of the hydrolysates indicates the role of auxiliary oxidative enzymes present in A. terreus and A. strumarium secretomes for enhancing the capability of the cellulolytic cocktails. The paper further demonstrate positive effect of using the cocktails for enhanced saccharification and subsequent fermentation to ethanol of acid pre-treated rice straw, corn residues and sugarcane bagasse at higher substrate loading rates (20% w/v). The paper also reports co-utilization of composite sugars derived from molasses and enzymatic hydrolysate obtained from agnostic lignocellulosics for efficient bioconversion to ethanol applicable for developing BOLT-ON technology.

Potential of oleaginous yeast Trichosporon sp., for conversion of sugarcane bagasse hydrolysate into biodiesel

This study reports production of microbial oil from a yeast strain Trichosporon sp., (RW) isolated from decayed wood. Preliminary analysis based on fluorescence microscopy and spectroscopy of Nile red stained yeast cells showed accumulation of lipid globules. The potential of the yeast to produce lipids was evaluated on glucose, glycerol and acid hydrolysate of sugarcane bagasse, where Trichosporon sp. (RW) was found to accumulate 21.45 (59.6%), 18.41 (56%) and 10.25g/l (40.5%) of the lipids after 120h of fermentation at 30°C. FAME analysis of lipids by GC-FID and NMR revealed oleic acid (18:1) as the major constituent, corresponding to 50.05, 46.48 and 54.66% of the accumulated lipids in glucose, glycerol and hydrolysate grown cultures, respectively. Other accumulated lipids included palmitic (16:0), linoleic (18:2) and stearic acids (18:0) in that order. The cetane number of the lipids ranged from 52.39 to 59.57 indicating suitability for biodiesel production.

Evaluation of secretome of highly efficient lignocellulolytic Penicillium sp. Dal 5 isolated from rhizosphere of conifers

Penicillium sp. (Dal 5) isolated from rhizosphere of conifers from Dalhousie (Himachal Pradesh, India) was found to be an efficient cellulolytic strain. The culture under shake flask on CWR (cellulose, wheat bran and rice straw) medium produced appreciably higher levels of endoglucanase (35.69U/ml), β-glucosidase (4.20U/ml), cellobiohydrolase (2.86U/ml), FPase (1.2U/ml) and xylanase (115U/ml) compared to other Penicillium strains reported in literature. The mass spectroscopy analysis of Penicillium sp. Dal 5 secretome identified 108 proteins constituting an array of CAZymes including glycosyl hydrolases (GH) belonging to 24 different families, polysaccharide lyases (PL), carbohydrate esterases (CE), lytic polysaccharide mono-oxygenases (LPMO) in addition to swollenin and a variety of carbohydrate binding modules (CBM) indicating an elaborate genetic potential of this strain for hydrolysis of lignocellulosics. Further, the culture extract was evaluated for hydrolysis of alkali treated rice straw, wheat straw, bagasse and corn cob at 10% substrate loading rate.

Malbranchea cinnamomea: A thermophilic fungal source of catalytically efficient lignocellulolytic glycosyl hydrolases and metal dependent enzymes

This study reports thermophilic fungus Malbranchea cinnamomea as an important source of lignocellulolytic enzymes. The secretome analysis using LC-MS/MS orbitrap showed that fungus produced a spectrum of glycosyl hydrolases (cellulase/hemicellulase), polysaccharide lyases (PL) and carbohydrate esterases (CE) in addition to cellobiose dehydrogenase (CDH) indicating the presence of functional classical and oxidative cellulolytic mechanisms. The protein fractions in the secretome resolved by ion exchange chromatography were analyzed for ability to hydrolyze alkali treated carrot grass (ATCG) in the presence of Mn(2+)/Cu(2+). This strategy in tandem with peptide mass fingerprinting led to identification of metal dependent protein hydrolases with no apparent hydrolytic activity, however, showed 5.7 folds higher saccharification in presence of Mn(2+). Furthermore, adding different protein fractions to commercial cellulase (Novozymes: Cellic CTec2) resulted in enhanced hydrolysis of ATCG ranging between 1.57 and 3.43 folds indicating the enzymes from M. cinnamomea as catalytically efficient.

Evaluation of glycosyl hydrolases from thermophilic fungi for their potential in bioconversion of alkali and biologically treated Parthenium hysterophorus weed and rice straw into ethanol

The aim of this work was to evaluate glycosyl hydrolases produced by diverse thermophilic fungal strains for saccharification of alkali and biologically (Trametes hirusita/Myrothecium roridum) treated Parthenium hysterophorus and rice straw. The compositional analysis of hydrolysates by HPLC showed distinct profiles of hexose, pentose and oligomeric sugars. Malbranchea cinnamomea was most efficient source of glycosyl hydrolases producing 283.8, 35.9, 129.6, 27,193, 4.66, 7.26(units/gds) of endoglucanase, cellobiohydrolase, β-glucosidase, xylanase, α-αrabinofuranosidase and β xylosidase, respectively. The saccharification of alkali and biologically treated carrot grass by culture extract of M. cinnamomea was further enhanced by supplementation of β-glucosidase produced by Aspergillus sp. mutant "O". The resultant hydrolysates containing glucose/xylose were fermented efficiently to ethanol by Saccharomyces cerevisiae owing to presence of xylose isomerase (0.8 units/gds) activity in culture extract of M. cinnamomea resulting in production of 16.5 and 15.0 g/l of ethanol from alkali treated rice straw and carrot grass, respectively.

Enhanced cellulase producing mutants developed from heterokaryotic Aspergillus strain

A heterokaryon 28, derived through protoplast fusion between Aspergillus nidulans and Aspergillus tubingensis (Dal8), was subjected cyclic mutagenesis followed by selection on increasing levels of 2-deoxy glucose (2-DG) as selection marker. The derived deregulated cellulase hyper producing mutant '64', when compared to fusant 28, produced 9.83, 7.8, 3.2, 4.2 and 19.74 folds higher endoglucanase, β-glucosidase, cellobiohydrolase, FPase and xylanase, respectively, under shake cultures. The sequence analysis of PCR amplified β-glucosidase gene from wild and mutant showed nucleotide deletion/substitution. The mutants showed highly catalytic efficient β-glucosidase as evident from low Km and high Vmax values. The expression profiling through zymogram analysis also indicated towards over-expression of cellulases. The up/down regulated expressed proteins observed through SDS-PAGE were identified by Peptide mass fingerprinting The cellulase produced by mutants in conjunction with cellulase free xylanase derived from Thermomyces lanuginosus was used for efficient utilization of alkali treated rice straw for obtaining xylo-oligosaccharides and ethanol.

Statistical Optimization of Medium Components for Mass Production of Plant Growth-Promoting Microbial Inoculant Pseudomonas trivialis BIHB 745 (MTCC5336)

Optimizing nutritional requirements for mass production of microbial inoculants in shortened time has relevance for their economical field application. Therefore, the present study aimed at selecting suitable growth medium, optimizing its components, and up-scaling inoculum production for plant growth-promoting Pseudomonas trivialis BIHB 745. Of the different media tested, the culture exhibited maximal viable colony count in trypticase soya broth with 17.6 % increased biomass on optimizing levels of carbon source, nitrogen source, and NaCl using response surface methodology. A twofold higher biomass with 9 h shorter incubation period was obtained in optimized medium in a bioreactor in comparison to shake flasks.

Ethanol production from alkali-treated rice straw via simultaneous saccharification and fermentation using newly isolated thermotolerant Pichia kudriavzevii HOP-1

In this study, simultaneous saccharification and fermentation (SSF) was employed to produce ethanol from 1% sodium hydroxide-treated rice straw in a thermostatically controlled glass reactor using 20 FPU gds⁻¹ cellulase, 50 IU gds⁻¹ β-glucosidase, 15 IU gds⁻¹ pectinase and a newly isolated thermotolerant Pichia kudriavzevii HOP-1 strain. Scanning electron micrograph images showed that the size of the P. kudriavzevii cells ranged from 2.48 to 6.93 μm in diameter while the shape of the cells varied from oval, ellipsoidal to elongate. Pichia kudriavzevii cells showed extensive pseudohyphae formation after 5 days of growth and could assimilate sugars like glucose, sucrose, galactose, fructose, and mannose but the cells could not assimilate xylose, arabinose, cellobiose, raffinose, or trehalose. In addition, the yeast cells could tolerate up to 40% glucose and 5% NaCl concentrations but their growth was inhibited at 1% acetic acid and 0.01% cyclohexamide concentrations. Pichia kudriavzevii produced about 35 and 200% more ethanol than the conventional Saccharomyces cerevisiae cells at 40 and 45°C, respectively. About 94% glucan in alkali-treated rice straw was converted to glucose through enzymatic hydrolysis within 36 h. Ethanol concentration of 24.25 g l⁻¹ corresponding to 82% theoretical yield on glucan basis and ethanol productivity of 1.10 g l⁻¹ h⁻¹ achieved using P. kudriavzevii during SSF hold promise for scale-up studies. An insignificant amount of glycerol and no xylitol was produced during SSF. To the best of our knowledge, this is the first study reporting ethanol production from any lignocellulosic biomass using P. kudriavzevii.

Cytotoxic and apoptotic activity of essential oil from Ocimumviride towards COLO 205 cells

We investigated the apoptosis inducing effect of essential oil (EO) from aerial parts of Ocimumviride in human colorectal adenocarcinoma cells (COLO 205 cell line). The COLO 205 cells were exposed to 0.0125-0.1 microl/ml of EO for 24, 48 and 72h. Growth inhibition was determined by sulphorhodamine B (SRB) assay. Double staining with acridine orange and ethidium bromide for nuclear changes was performed. Cell cycle analysis and change in mitochondrial membrane potential was quantified by flow cytometry. Subsequently, using annexin V/PI assay, the proportion of cells actively undergoing apoptosis was determined. Changes in DNA were observed by DNA ladder assay. Eventually the surface morphology of apoptotic cells was studied by scanning electron microscopy. EO is cytotoxic to COLO 205 cells in dose and time-dependent manner, as is evident by SRB assay. This observed cell death was due to apoptosis, as established by annexin V/PI assay, DNA ladder formation and scanning electron microscopy. Our results reveal that EO has apoptosis inducing effect against COLO 205 cells in vitro and is a promising candidate for further anti-cancer study.

Profiling differential expression of cellulases and metabolite footprints in Aspergillus terreus

This study reports differential expression of endoglucanase (EG) and beta-glucosidase (betaG) isoforms of Aspergillus terreus. Expression of multiple isoforms was observed, in presence of different carbon sources and culture conditions, by activity staining of poly acrylamide gel electrophoresis gels. Maximal expression of four EG isoforms was observed in presence of rice straw (28 U/g DW substrate) and corn cobs (1.147 U/ml) under solid substrate and shake flask culture, respectively. Furthermore, the sequential induction of EG isoforms was found to be associated with the presence of distinct metabolites (monosaccharides/oligosaccharides) i.e., xylose (X), G(1), G(3) and G(4) as well as putative positional isomers (G(1)/G(2), G(2)/G(3)) in the culture extracts sampled at different time intervals, indicating specific role of these metabolites in the sequential expression of multiple EGs. Addition of fructose and cellobiose to corn cobs containing medium during shake flask culture resulted in up-regulation of EG activity, whereas addition of mannitol, ethanol and glycerol selectively repressed the expression of three EG isoforms (Ia, Ic and Id). The observed regulation profile of betaG isoforms was distinct when compared to EG isoforms, and addition of glucose, fructose, sucrose, cellobiose, mannitol and glycerol resulted in down-regulation of one or more of the four betaG isoforms.

Screening and selection of lovastatin hyper-producing mutants of Aspergillus terreus using cyclic mutagenesis

134 fungal cultures isolated from different soil samples were screened for lovastatin production. Of these, 38 isolates produced different levels of lovastatin. An Aspergillus terreus strain GD13, producing 190 mg/l of lovastatin was selected and subjected to a rational mutation-selection programme based on the resistance to lovastatin and fatty acid synthase (FAS) inhibitors, viz., iodoacetamide and N-ethylmaleimide. After three cycles of mutagenesis, a hyper-producing mutant (EM19) exhibiting 7.5-fold (1424 mg/l) higher levels of lovastatin when compared to wild type parent strain was obtained.

Production, purification and characterization of thermostable phytase from thermophilic fungus Thermomyces lanuginosus TL-7

Ten different strains of Thermomyces lanuginosus, isolated from composting soils were found to produce phytase when grown on PSM medium. The wild type strain CM was found to produce maximum amount ofphytase (4.33 units/g DW substrate). Culturing T. lanuginosus strain CM on medium containing wheat bran and optimizing other culture conditions (carbon source, media type, nitrogen source, level of nitrogen, temperature, pH, inoculum age, inoculum level and moisture), increased the phytase yield to 13.26 units/g substrate. This culture was further subjected to UV mutagenesis for developing phytase hyperproducing mutants. The mutant (TL-7) showed 2.29-fold increase in phytase activity as compared to the parental strain. Employing Box-Behnken factor factorial design of response surface methodology resulted in optimized phytase production (32.19 units/g of substrate) by mutant TL-7. A simple two-step purification (40.75-folds) ofphytase from mutant TL-7 was achieved by anion exchange and gel filtration chromatography. The purified phytase (approximately 54 kDa) was characterized to be optimally active at pH 5.0 and temperature 70 degrees C, though the enzyme showed approximately 70% activity over a wide pH and temperature range (2.0-10.0 and 30-90 degrees C, respectively). The phytase showed broad substrate specificity with activity against sodium phytate, ADP and riboflavin phosphate. The phytase from T. lanuginosus was thermoacidstable as it showed up to 70% residual activity after exposure to 70 degrees C at pH 3.0 for 120 min. The enzyme showed Km 4.55 microM and Vmax 0.833 microM/min/mg against sodium phytate as substrate.

Role of Transglycosylation Products in the Expression of Multiple Xylanases in Myceliophthora sp. IMI 387099

This study reports the regulation of multiple xylanases produced by Myceliophthora sp. IMI 387099. Fructose was found to positively regulate the expression of multiple xylanase when used as sole carbon source. The xylanases (EX(1 )and EX(2)) of acidic pI were expressed in the presence of simple sugars (glucose, arabinose, and xylose), whereas xylanase of both acidic as well as basic pI (EX(1,) EX(2,) EX(3), and EX(5)) were expressed in the presence of fructose, xylan, and combination of xylan and alcohol. The combination of fructose and xylan also led to expression of an additional xylanase (EX(4)). The positional isomer (iso-X4) was found to be the key transglycosylation product when cultures were grown in the presence of fructose and xylan. In the presence of alcohols, the higher expression of xylanase was ascribed to the synergistic effect of alkyl glycoside and other transglycosylation products present in the culture extracts.

Production of multiple xylanolytic and cellulolytic enzymes by thermophilic fungus Myceliophthora sp. IMI 387099

This study reports the production of xylanolytic and cellulolytic enzymes by a thermophilic fungal isolate Myceliophthora sp. using a cheap medium containing rice straw and chemically defined basal medium under solid-state culture. A combination of one factor at a time approach followed by response surface methodology using Box-Behnken design of experiments resulted in 2.5, 1.25, 1.28 and 4.23 fold increase in xylanase, endoglucanase, beta-glucosidase and FPase activity, respectively. The zymograms developed against IEF gels showed that multiple isoforms of xylanase (5), endoglucanase (4) and beta-glucosidase (2) were produced under optimized culture conditions. Moreover, thiol containing serine proteases produced during the growth of the culture had no role in the post-translational modification of these xylanases.

Production and characterization of thermostable alkaline phytase from Bacillus laevolacticus isolated from rhizosphere soil

A novel phytase producing thermophilic strain of Bacillus laevolacticus insensitive to inorganic phosphate was isolated from the rhizosphere soil of leguminous plant methi (Medicago falacata). The culture conditions for production of phytase by B. laevolacticus under shake flask culture were optimized to obtain high levels of phytase (2.957 +/- 0.002 U/ml). The partially purified phytase from B. laevolacticus strain was optimally active at 70 degrees C and between pH 7.0 and pH 8.0. The enzyme exhibited thermostability with approximately 80% activity at 70 degrees C and pH 8.0 for up to 3 h in the presence/absence of 5 mM CaCl(2). The phytase from B. laevolacticus showed high specificity for phytate salts of Ca(+) > Na(+). The enzyme showed an apparent K (m) 0.526 mM and V (max) 12.3 mumole/min/mg of activity against sodium phytate.

Sorghum straw for xylanase hyper-production by Thermomyces lanuginosus (D2W3) under solid-state fermentation

This paper reports the production of very high levels of cellulase free xylanase and associated hemicellulases by an indigenous thermophilic isolate of Thermomyces lanuginosus (D(2)W(3)) using solid-state fermentation. Sorghum straw, an inexpensive and abundant source of carbon supported maximal xylanase activity (11,855 units/g dry substrate). Culturing T. lanuginosus D(2)W(3) on sorghum straw and optimizing other culture conditions (media types, particle size of carbon source, inoculum level, inoculum age and additives), yielded increased levels of xylanase (39,726 units/g dry substrate). Further optimization of enzyme production was carried out using Box-Behnken design of experiments with three independent variables (inoculum level, glycerol and ammonium sulphate concentrations) which resulted in very high levels of xylanase, 48,000+/-1774 units/g dry substrate, and 2.6+/-0.2, 13.4+/-0.56, 68+/-1.7, 1.4+/-0.08, 1.2+/-0.05 (units/g dry substrate) of beta-xylosidase, alpha-galactosidase, pectinase, beta-mannosidase and alpha-L-arabinofuranosidase, respectively.

Constitutive α-amylase producing mutant and recombinant haploid strains of thermophilic fungusThermomyces lanuginosus

Morphological, developmental and antimetabolite-resistant mutants of T. lanuginosus were characterized and used for screening with the aim to develop constitutive alpha-amylase-hyperproducing strains. The protoplast fusion of two spontaneous mutants of T. lanuginosus, characterized as asporulating and resistant to 2-deoxy-D-glucose (2DG), resulted in sporulating, 2DG sensitive heterokaryotic fusants. A recombinant haploid strain F64fB developed there from produced alpha-amylase constitutively in glucose-containing medium. Constitutive alpha-amylase-hyperproducing mutant (III8) obtained after cyclic mutagenesis and screening yielded approximately 20 fold more alpha-amylase in a glycerol-containing medium than the wild strain.

Biological treatment of textile dye Acid violet-17 by bacterial consortium in an up-flow immobilized cell bioreactor

AIMS

To develop a cost effective and efficient biological treatment process for small scale textile processing industries (TPI) releasing untreated effluents containing intense coloured Acid violet-17 (AV-17), a triphenyl methane (TPM) group textile dye.

METHODS AND RESULTS

The samples collected from effluent disposal sites of TPI were used for selective enrichment of microbial populations capable of degrading/decolourizing AV-17. A consortium of five bacterial isolates was used to develop an up-flow immobilized cell bioreactor for treatment of feed containing AV-17. The bioreactor, operating at a flow rate of 6 ml x h(-1), resulted in 91% decolourization of 30 mg AV-17/l with 94.3 and 95.7% removal of biochemical oxygen demand and chemical oxygen demand of the feed. Comparison of the input and output of the bioreactor by UV-visible, thin layer chromatography and (1)H-nuclear magnetic resonance spectroscopy indicates conversion of the parent dye into unrelated metabolic intermediates.

SIGNIFICANCE

These results will form a basis for developing 'on-site' treatment system for TPI effluents to achieve decolourization and degradation of residual dyes.

Biodegradation of acid blue-15, a textile dye, by an up-flow immobilized cell bioreactor

Acid blue-15, a complex and resonance-stabilized triphenylmethane (TPM) textile dye, resistant to transformation, was decolorized/degraded in an up-flow immobilized cell bioreactor. A consortium comprised of isolates belonging to Bacillus sp., Alcaligenes sp. and Aeromonas sp. formed a multispecies biofilm on refractory brick pieces used as support material. The TPM dye was degraded to simple metabolic intermediates in the bioreactor with 94% decolorization at a flow rate of 4 ml h(-1).

Amylase hyperproduction by deregulated mutants of the thermophilic fungus Thermomyces lanuginosus

Thermomyces lanuginosus was subjected to three cycles of mutagenesis (UV/NTG) and a selection procedure to develop amylase-hyperproducing, catabolite-repression-resistant and partially constitutive strains. One of the selected derepressed mutant strain III(51), produced approximately 7- and 3-fold higher specific activity of alpha-amylase (190 U/mg protein) and glucoamylase (105 U/mg protein), respectively, compared to a wild-type parental strain. Further, the effect of production parameters on mutant strain III(51) was studied using a Box-Behnken design. The regression models computed showed significantly high R(2) values of 96 and 97% for alpha-amylase and glucoamylase activities, respectively, indicating that they are appropriate for predicting relationships between corn flour, soybean meal and pH with alpha-amylase and glucoamylase production.

Amylase hyper-producing haploid recombinant strains of Thermomyces lanuginosus obtained by intraspecific protoplast fusion

Amylase hyper-producing, catabolite-repression-resistant, recombinant strains were produced by intraspecific protoplast fusion of thermophilic fungus Thermomyces lanuginosus strains, using well-characterized, morphological, and 2-deoxy-D-glucose resistant markers. The fusant heterokaryons exhibited enhanced amylase activities as compared to the amylase hyper-producing parental strain (T2). Diploids derived from heterokaryons segregated to stable haploid recombinant strains. In the haploid strain (Tlh 4q), approximately 5-fold higher specific activities of alpha-amylase and glucoamylase in the culture filtrate were observed as compared to the wild-type strain (W0).

Shake culture studies for the production of amylases by Thermomyces lanuginosus

The paper describes shake flask culture optimization studies for the production of amylases by Thermomyces lanuginosus. The culture was found to produce maximally alpha-amylase and glucoamylase (18.4 & 11.2 units/ml), respectively when the medium contained rice flour (2% w/v) as carbon and corn steep liquor as nitrogen source with medium pH adjusted to 5.5 and incubated for 72 h under shaking conditions (150 rpm) at 50 degrees C.