Co-immobilization of amylases in porous crosslinked gelatin matrices by different reticulations approaches.

The aim of this study was to carry out the co-immobilization of α-amylase and glucoamylase in crosslinked gelatin porous supports. For this, two methods of co-immobilization were proposed based on the crosslinking with glutaraldehyde (Ggta) or CaCl2 in presence of alginate (Gcal). The supports characterization revealed a porous microstructure with good interaction between its components according to the FTIR analysis and thermal properties. Optimal pH and temperature of the Gcal co-immobilized enzymes were determined at 60 °C and pH 6.0, present an enzymatic activity of 120 µmol·mL·min-1. Moreover, both supports were reused for up to 8 hydrolysis cycles. In addition, co-immobilized enzymes were more efficient than free enzymes in starch saccharification of starch in the long term. These results reveal that the co-immobilization of amylases in gelatinous supports is a promising approach in enzymatic chain reactions.

Produção de biossurfactantes: manoproteínas intracelulares e soforolipídios extracelulares por Saccharomyces cerevisiae / Biosurfactant production: intracellular manoproteins and extracellular sophorolipids by Saccharomyces cerevisiae

RESUMO Os biossurfactantes apresentam inúmeras aplicações ambientais e são produzidos por diversos microrganismos. Os provenientes da levedura Saccharomyces cerevisiae são pouco estudados para fins ambientais, sendo atóxicos. Objetivou-se o estudo da produção de biossurfactantes intra e extracelular por essa levedura, desenvolvida em meio de cultivo contendo 0,5% de extrato de levedura e 1% de peptona, além de concentrações variadas de sacarose e indutores oleosos - glicerol e óleos de soja e diesel. Os experimentos foram realizados durante 96 horas, e a produção de biossurfactantes foi avaliada diariamente, por meio da redução da tensão superficial e de estabilização de emulsões. O biossurfactante extracelular foi extraído da biomassa obtida, com posterior precipitação e caracterização química por intermédio de espectrometria de massa. As maiores produtividades de emulsificantes extracelulares foram obtidas com glicerol (0,20 UE.h-1) e óleo de soja (0,21 UE.h-1), em 48 horas de cultivo. Em ensaios posteriores, realizados com aumento da concentração de indutor, foi verificado um aumento das produtividades extracelulares para 0,45 UE.h-1 para o glicerol e 0,30 UE.h-1 para o óleo de soja. A maior redução da tensão superficial foi de 9,89%, em 72 horas, para o indutor óleo diesel. A diminuição dessa tensão, aliada ao aumento das atividades emulsificantes, é um importante indicativo da utilização do substrato hidrofóbico pelo microrganismo. O estudo comprova aumento na produção de biossurfactantes extracelulares quando realizada otimização de cultivo. Para a produção dos intracelulares, a necessidade de processo de rompimento celular aumenta os custos do bioprocesso.

ABSTRACT Biosurfactants implicate many environmental applications, being produced by a wide range of microorganisms. Those from the Saccharomyces cerevisiae yeast are still poorly studied for environmental purposes and are non-toxic. The aim of the study was the production of intra- and extracellular biosurfactants by the Saccharomyces cerevisiae yeast. The yeast was grown in cultured medium containing 0.5% yeast extract, 1% peptone and variable concentrations of sucrose and oily inducers. Inducers used were glycerol, soybean oil and diesel oil. Experiments were conducted for 96 h, and the daily production of biosurfactants was evaluated by reducing surface tension and stabilizing emulsions. Extracellular biosurfactant was extracted from the obtained biomass, with subsequent precipitation and chemical characterization by mass spectrometry. The highest extracellular emulsifier yields were achieved with glycerol inductor (0.20 UE h-1) and soybean oil (0.21 UE h-1) in 48h of cultivation. In later tests performed with increasing concentration of inducer, an increase in extracellular yields was noticed in these experiments (0.45 UE h-1 for glycerol and 0.30 UE h-1 for the soybean oil). The greatest reduction in surface tension was 9.89% in 72 h for diesel oil inducer. The reduction of surface tension combines with the increase of emulsifying activities in an important indicator of the use of hydrophobic substrate by the microorganism. The study confirms an increase in the production of extracellular biosurfactants when optimizing cultivation. The production of intracellular biosurfactants has also been verified, however the process of cellular disruption increases the cost of the bioprocess.

Bioethanol from Spirulina platensis biomass and the use of residuals to produce biomethane: An energy efficient approach.

This study aimed to produce bioethanol using Spirulina platensis biomass and the use of saccharification and fermentation wastes of bioethanol production to produce biomethane. The potential for energy generation in each technological route was quantified. Both, the enzymatic hydrolysis of the microalgae polysaccharides and the fermentation process, presented efficiencies above 80%. The fermentation of the hydrolyzate into ethanol was possible without the addition of synthetic nutrients to the must. The direct conversion of Spirulina biomass to biomethane had an energy potential of 16,770 kJ.kg-1, while bioethanol production from the hydrolysed biomass presented 4,664 kJ.kg-1. However, the sum of the energy potential obtained by producing bioethanol followed by the production of biomethane with the saccharification and fermentation residues was 13,945 kJ.kg-1. Despite this, the same raw material was able to produce both biofuels, demonstrating that Spirulina microalgae is a promising alternative to contribute in the field of renewable energies.

Saccharification of Spirulina platensis biomass using free and immobilized amylolytic enzymes.

We aimed to use physical methods of microalgal biomass rupture to study saccharification strategies using free and immobilized amylolytic enzymes. The biomass of Spirulina platensis, which consists of 50-60% carbohydrates, was exposed to physical cell rupture treatments, with better results obtained using freeze/thaw cycles following by gelatinization. In saccharification tests, it was possible to hydrolyze Spirulina biomass with hydrolysis efficiencies above 99% and 83%, respectively, using 1% (v/v) of free enzymes or 1% (m/v) of amylolytic enzymes immobilized together. The use of free and immobilized enzymes yielded high levels of conversion of polysaccharides to simple sugars in Spirulina biomass, showing that these processes are promising for the advancement of bioethanol production using microalgal biomass.

Spirulina platensis biomass composition is influenced by the light availability and harvest phase in raceway ponds.

The behavior of cyanobacteria and its potential use for biofuel production in scale-up conditions is a topic of growing importance. The aim of our work is to study the effects of illumination, stirring, and different growth phases on the cultivation of the cyanobacteria Spirulina platensis in 10 L raceways. The cultivations were carried out in a greenhouse under measured, but not controlled, illumination and in agitated raceways with stirring speeds varying from 0.1 to 0.4 m s-1, using culture media with nutrient depletion. At the end of the stationary phase (SP) and decline of culture, the biomass was harvested and used to determine the chemical composition. The stirring rate and the growing phase influenced the carbohydrate concentration. In both phases of cultivation, compared to high-speed stirring, stirring at lower speeds produced fewer carbohydrates in the culture. Biomass grown until the end of the SP with a stirring speed of 0.35 m s-1 had a carbohydrate content of 72%, which is very high compared to that reported in the literature.

Spirulina platensis is more efficient than Chlorella homosphaera in carbohydrate productivity.

This study aimed to compare the production of biomass with high carbohydrate content by Spirulina platensis LEB 52 and Chlorella homosphaera microalgae. The cultivation of C. homosphaera and S. platensis LEB 52 was performed in standard medium diluted at 50%, and glucose was added as a source of organic carbon for mixotrophic metabolism. The sodium nitrate concentration was increased and the nitrogen components were reduced in the media to induce the synthesis of carbohydrates. C. homosphaera and S. platensis LEB 52 produced 16.32 and 116 mg L-1 of carbohydrates per day, respectively, when cultivated with 50% less nitrogen and 20% and 10% more sodium chloride, compared with the control. Glucose addition was an essential factor for microalgal growth, resulting in biomass increases of up to 2.79- and 3.45-fold for C. homosphaera and S. platensis LEB 52, respectively. Spirulina presented better characteristics than Chlorella with regard to the capacities of growth and carbohydrate synthesis.

Increase in the carbohydrate content of the microalgae Spirulina in culture by nutrient starvation and the addition of residues of whey protein concentrate.

Non-renewable sources that will end with time are the largest part of world energy consumption, which emphasizes the necessity to develop renewable sources of energy. This necessity has created opportunities for the use of microalgae as a biofuel. The use of microalgae as a feedstock source for bioethanol production requires high yields of both biomass and carbohydrates. With mixotrophic cultures, wastewater can be used to culture algae. The aim of the study was to increase the carbohydrate content in the microalgae Spirulina with the additions of residues from the ultra and nanofiltration of whey protein. The nutrient deficit in the Zarrouk medium diluted to 20% and the addition of 2.5% of both residue types led to high carbohydrate productivity (60 mg L(-1) d(-1)). With these culture conditions, the increase in carbohydrate production in Spirulina indicated that the conditions were appropriate for use with microalgae as a feedstock in the production of bioethanol.