Synergistic integration of wastewaters from second generation ethanol plant for algal biofuel production: an industrially relevant option.

The present study provides an integrated method for utilizing the wastewaters from second generation (2G) ethanol pretreatment plant for microalgal biomass and lipid production. The study was conducted using a mixture of wastewaters (referred as MW; pH 4.3) generated after washing of acidic and alkaline-soaked lignocellulosic biomass prior to pretreatment process. The growth studies indicated that the thermotolerant strain of Chlorella pyrenoidosa (C. pyrenoidosa) M18 exhibited higher cell proliferation in wastewater as compared to freshwater. About 20-25% enhancement in biomass (509 mg L-1 d-1 ± 3.09) and lipid productivity (146 mg L-1 d-1 ± 1.34) was observed in MW. The total chlorophyll content and variable fluorescence by maximum fluorescence (Fv/Fm) ratio of strain cultivated in MW were 10.32 µg mL-1 and 0.75, respectively. The use of MW also enhanced the content of saturated and monounsaturated fatty acids in total lipid. The exhausted wastewater medium obtained after harvesting the auto-flocculated biomass was also reused up to three successive growth cycles. The recycled medium without any nutrient addition could be used for two subsequent rounds with enhanced biomass (520 mg L-1 d-1 ± 4.07) and lipid (157.71 mg L-1 d-1 ± 1.09) productivities. This synergistic approach of cultivating thermotolerant microalgae with wastewater from 2G pretreatment plant provides an economical setup for development of commercial algal biofuel technology.

A screening approach for assessing lytic polysaccharide monooxygenase activity in fungal strains.

BACKGROUND: Efforts to develop efficient lignocellulose-degrading enzymatic preparations have led to the relatively recent discovery of a new class of novel cellulase boosters, termed lytic polysaccharide monoxygenases (LPMOs). These enzymes are copper-dependent metalloenzymes that initiate the biomass deconstruction process and subsequently work together with cellulases, hemicellulases, and other accessory enzymes to enhance their hydrolytic action. Given their wide distribution and diversity, screening and isolation of potent LPMOs from natural fungal diversity may provide an important avenue for increasing the efficiency of cellulases and thereby decreasing cellulosic ethanol production costs. However, methods for quick screening and detection are still not widely available. In this article, a simple and sensitive method is described by combining nonhydrolytic activity enhancement followed by LC-MS-based quantitation of LPMOs. RESULTS: In this study, a screening approach has been developed for the detection of nonhydrolytic cellulase-enhancing enzymes in crude fungal supernatants. With the application of a saturating benchmark cocktail of Celluclast 1.5L, fungal isolates were selected which had the capability of hydrolyzing pretreated rice straw by their synergistic enzyme fractions. Subsequently, these fungal extracts along with an LPMO-enriched commercial enzyme were investigated for their ability to produce Type I LPMO activity. An LC-MS-based methodology was applied to quantitate gluconic acid in enzymatic hydrolysates as an indirect measurement of Type I LPMO activity. CONCLUSION: The present study describes an LC-MS-based separation method to detect and quantitate LPMO activity in a commercial enzyme. This method was also applied to screen fungal extracts. The developed screening strategy has enabled detection of LPMO activity in two industrially important Penicillium strains.

Enhanced lipid production in thermo-tolerant mutants of Chlorella pyrenoidosa NCIM 2738.

The present study aimed to develop thermo-tolerant mutants of Chlorella pyrenoidosa NCIM 2738 for high lipids production. For this, ethyl methane sulfonate was used, which generated two effective thermo-tolerant mutants, M18 and M24 of Chlorella pyrenoidosa NCIM 2738, capable of surviving at temperature up to 47°C and showing improved lipid and biomass yields. They showed 59.62% and 50.75% increase, respectively in lipid content compared to wild type at 30°C, which could not grow at temperature above 35°C. The novelty of this study lied in incorporation of PAM Flurometry with mutagenesis to generate thermo-tolerant mutants of C. pyrenoidosa and investigating the reasons for increased yields of mutants at cellular and photosynthetic levels with the aim to use them for commercial biodiesel production.

Kinetic modeling of growth and lipid body induction in Chlorella pyrenoidosa under heterotrophic conditions.

The aim of the present work was to develop a mathematical model to describe the biomass and (total) lipid productivity of Chlorella pyrenoidosa NCIM 2738 under heterotrophic conditions. Biomass growth rate was predicted by Droop's cell quota model, while changes observed in cell quota (utilization) under carbon excess conditions were used for the modeling and predicting the lipid accumulation rate. The model was simulated under non-limiting (excess) carbon and limiting nitrate concentration and validated with experimental data for the culture grown in batch (flask) mode under different nitrate concentrations. The present model incorporated two modes (growth and stressed) for the prediction of endogenous lipid synthesis/induction and aimed to predict the effect and response of the microalgae under nutrient starvation (stressed) conditions. MATLAB and Genetic Algorithm were employed for the prediction and validation of the model parameters.