Advances in microalgal research for valorization of industrial wastewater.

This review article focuses on recent updates on remediation of industrial wastewater (IWW) through microalgae cultivation. These include how adding additional supplements of nutrient to some specific IWWs lacking adequate nutrients improving the microalgae growth and remediation simultaneously. Various pretreatments strategy recently employed for IWWs treatment other than dealing with microalgae was discussed. Various nutrient-rich IWW could be utilized directly with additional dilution, supplement of nutrients and without any pretreatment. Recent advances in various approaches and new tools used for cultivation of microalgae on IWW such as two-step cultivation, pre-acclimatization, novel microalgal-bioelectrical systems, integrated catalytic intense pulse-light process, sequencing batch reactor, use of old stabilized algal-bacterial consortium, immobilized microalgae cells, microalgal bacterial membrane photobioreactor, low-intensity magnetic field, BIO_ALGAE simulation tool, etc. are discussed. In addition, biorefinery of microalgal biomass grown on IWW and its end-use applications are reviewed.

Development of eco-friendly process for the production of bioethanol from banana peel using inhouse developed cocktail of thermo-alkali-stable depolymerizing enzymes.

Conversion of agro-industrial wastes to energy is an innovative approach for waste valorization and management which also mitigates environmental pollution. In this view, present study investigated the feasibility of producing bioethanol from banana peels using cocktail of depolymerizing enzyme/s. We isolated Geobacillus stearothermophilus HPA19 from natural resource which produces cocktail of thermo-alkali-stable xylano-pectino-cellulolytic enzyme/s using wheat bran within 24 h. The optimal temperature and pH for xylanase, filter paper cellulase and pectinase were 80, 70 and 80 °C, and 9.0, 8.0 and 9.0, respectively. Cocktail enzymes showed stability at high temperature (80 °C) and pH (10.0). Ni2+ and Zn2+ promoted the relative activity of xylanase and FPase, whereas Na+, Ca2+ and K+ promoted pectinase activity. Cocktail was assessed in saccharification of banana peel. Reducing sugar obtained (37.06 mg ml-1) after one variable at a time (OVAT) method is greatly influenced by enzyme dose. Further, response surface methodology was used to optimize saccharification leading to twofold increase in reducing sugar. Maximum ethanol production (21.1 gl-1) was achieved through fermentation giving the efficiency of 76.5% within 30 h. Hence utilization of waste biomass for production of value-added products through biotechnological intervention not only helps to combat environmental pollution but also contributes significantly to the economy.

Agrobacterium tumefaciens-mediated genetic transformation of haptophytes (Isochrysis species).

Isochrysis galbana and Isochrysis sp. are economically important microalgae from the division of haptophytes. Here, we report Agrobacterium-mediated stable DNA transfer into their nuclear genomes. Initial studies were performed to standardize co-cultivation media and determine the sensitivity of the microalgae to selective agents. Up to 1 mg/ml of the antibiotic hygromycin did not inhibit growth, whereas both the haptophytes bleached in artificial seawater (ASW) medium containing micromolar concentrations of the herbicide norflurazon. Co-cultivation of Isochrysis sp. and I. galbana with Agrobacterium tumefaciens strain LBA 4404 harboring the binary vector pCAMBIA 1380-pds-L504R yielded norflurazon-resistant (NR) colonies visible on selective plates after 20-30 days. pCAMBIA 1380-pds-L540R was constructed by cloning a mutated genomic phytoene desaturase (pds) gene from Haematococcus pluvialis as a selectable marker gene into the binary vector system pCAMBIA 1380. Co-cultivation of Isochrysis sp. with A. tumefaciens in ASW medium containing 200 µM of acetosyringone for 72 h produced the highest number of NR cells. For I. galbana, 100 µM of acetosyringone, ASW medium, and 48 h co-cultivation period appeared to be optimum co-cultivation parameters. The NR colonies kept their resistance phenotype for at least 24 months, even in the absence of selective pressure. The transfer of the pds gene in NR cells was shown by PCR amplification of the T-DNA sequences from the genomic DNA of NR cells and Southern blot analysis using T-DNA sequences as probes. The genetic manipulation described here will allow metabolic engineering and a better understanding of several biochemical pathways in the future.

Physicochemical Properties of Roasted Soybean Flour Bioconverted by Solid-State Fermentation Using Bacillus subtilis and Lactobacillus plantarum.

To produce novel cheese-like fermented soybean, the solid-state fermentation of roasted soybean flour (RSF) was performed using 1.0% inoculum Bacillus subtilis HA and Lactobacillus plantarum, with the initial 60% substrate moisture for 10 hr at 42°C, resulting in pH 6.5, 0.82% acidity, 3.5% mucilage, 14.3 unit/g protease activity, 7.6 unit/g fibrinolytic activity, 216 mg% tyrosine content and 1.7×10(10) CFU/g of viable cell counts. After the second lactic acid fermentation with 10∼30% skim milk powder, the fermented RSF resulted in an increase in acidity with 1.64∼1.99%, tyrosine content with 246∼308 mg% and protease activity in the range of 5.2∼17.5 unit/g and 0.966 water activity. Viable cell counts as probiotics indicated 1.6×10(8) CFU/g of B. subtilis and 7.3×10(10) CFU/g of L. plantarum. The firmness of the first fermented RSF with 2,491 g·ømm(-1) greatly decreased to 1,533 g·ømm(-1) in the second fermented RSF, although firmness was slightly increased by adding a higher content of skim milk. The consistency of the second fermented RSF also decreased greatly from 55,640 to 3,264∼3,998 in the presence of 10∼30% skim milk. The effective hydrolysis of soy protein and skim milk protein in the fermented RSF was confirmed. Thus, the second fermented RSF with a sour taste and flavor showed similar textural properties to commercial soft cheese.

Utilization of tannery fleshings: Optimization of conditions for fermenting delimed tannery fleshings using Enterococcus faecium HAB01 by response surface methodology.

Conditions for fermentation of delimed tannery fleshings--to obtain higher degree of protein hydrolysis and reasonably better antioxidant activity--using Enterococcus faecium HAB01 (GenBank #FJ418568) were optimized. Three independent variables--viz., inoculum level (X1), glucose level (X2) and fermentation time (X3)--were optimized using response surface method considering degree of hydrolysis (DH; %) and total titrable acidity (TTA) as response variables. The optimized conditions were found to be 12.5% (v/w) inoculum, 17.5% (w/w) glucose and 96h of fermentation at 37+/-1 degrees C to obtain a maximum DH%. The usefulness of the predicted model was further validated by considering random combinations of the independent factors. The chemical score of the hydrolysate revealed an excess amount of essential amino acids, viz., arginine and leucine compared to reference protein. The liquor portion had relatively high antioxidant activities, indicating its potential for use as a high value feed ingredient.