Reinaldo Gaspar Bastos

COD and nitrogen removal from sugarcane vinasse by heterotrophic green algae Desmodesmus sp.

AbstractVinasse is the main wastewater from the ethanol fermentation–distillation process, generated in large volumes during industrial sugarcane processing. Desmodesmus is a green algae genus with recognized ability to treat wastewater containing organic matter and to consume nutrients under heterotrophic growth conditions. Thus, the aim of this research was to evaluate Desmodesmus sp. growth in sugarcane vinasse. Results indicated slight elevation of pH, low oxygen, and low carbon dioxide consumption. Nitrogen and chemical oxygen demand (COD) removal were 52.1 and 36.2%, respectively. Specific growth rate of 0.15xa0h−1 and high yield of COD to biomass at first hour (0.5xa0mgxa0mg−1) suggest the feasibility of biomass production of this green algae in sugarcane vinasse.

Microfluidic tools toward industrial biotechnology.

Microfluidics is a technology that operates with small amounts of fluids and makes possible the investigation of cells, enzymes, and biomolecules and encapsulation of biocatalysts in a greater variety of conditions than permitted using conventional methods. This review discusses technological possibilities that can be applied in the field of industrial biotechnology, presenting the principal definitions and fundamental aspects of microfluidic parameters to better understand advanced approaches. Specifically, concentration gradient generators, droplet‐based microfluidics, and microbioreactors are explored as useful tools that can contribute to industrial biotechnology. These tools present potential applications, inclusive as commercial platforms to optimizing in bioprocesses development as screening cells, encapsulating biocatalysts, and determining critical kinetic parameters.

The influence of process parameters in production of lipopeptide iturin A using aerated packed bed bioreactors in solid-state fermentation

The strain Bacillus iso 1 co-produces the lipopeptide iturin A and biopolymer poly-γ-glutamic acid (γ-PGA) in solid-state fermentation of substrate consisting of soybean meal, wheat bran with rice husks as an inert support. The effects of pressure drop, oxygen consumption, medium permeability and temperature profile were studied in an aerated packed bed bioreactor to produce iturin A, diameter of which was 50xa0mm and bed height 300xa0mm. The highest concentrations of iturin A and γ-PGA were 5.58 and 3.58xa0g/kg-dry substrate, respectively, at 0.4xa0L/min after 96xa0h of fermentation. The low oxygen uptake rates, being 23.34 and 22.56xa0mgxa0O2/kg-dry solid substrate for each air flow rate tested generated 5.75xa0W/kg-dry substrate that increased the fermentation temperature at 3.7xa0°C. The highest pressure drop was 561xa0Pa/m at 0.8xa0L/min in 24xa0h. This is the highest concentration of iturin A produced to date in an aerated packed bed bioreactor in solid-state fermentation. The results can be useful to design strategies to scale-up process of iturin A in aerated packed bed bioreactors. Low concentration of γ-PGA affected seriously pressure drop, decreasing the viability of the process due to generation of huge pressure gradients with volumetric air flow rates. Also, the low oxygenation favored the iturin A production due to the reduction of free void by γ-PGA production, and finally, the low oxygen consumption generated low metabolic heat. The results show that it must control the pressure gradients to scale-up the process of iturin A production.

A strain of Meyerozyma guilliermondii isolated from sugarcane juice is able to grow and ferment pentoses in synthetic and bagasse hydrolysate media.

The search for new microbial strains that are able to withstand inhibitors released from hemicellulosic hydrolysis and are also still able to convert sugars in ethanol/xylitol is highly desirable. A yeast strain isolated from sugarcane juice and identified as Meyerozyma guilliermondii was evaluated for the ability to grow and ferment pentoses in synthetic media and in sugarcane bagasse hydrolysate. The yeast grew in xylose, arabinose and glucose at the same rate at an initial medium pH of 5.5. At pH 4.5, the yeast grew more slowly in arabinose. There was no sugar exhaustion within 60xa0h. At higher xylose concentrations with a higher initial cell concentration, sugar was exhausted within 96xa0h at pH 4.5. An increase of 350xa0% in biomass was obtained in detoxified hydrolysates, whereas supplementation with 3xa0g/L yeast extract increased biomass production by approximately 40xa0%. Ethanol and xylitol were produced more significantly in supplemented hydrolysates regardless of detoxification. Xylose consumption was enhanced in supplemented hydrolysates and arabinose was consumed only when xylose and glucose were no longer available. Supplementation had a greater impact on ethanol yield and productivity than detoxification; however, the product yields obtained in the present study are still much lower when compared to other yeast species in bagasse hydrolysate. By the other hand, the fermentation of both xylose and arabinose and capability of withstanding inhibitors are important characteristics of the strain assayed.

Treatment of rice parboiling wastewater by cyanobacterium Aphanothece microscopica Nägeli with potential for biomass products

AbstractCyanobacterium Aphanothece microscopica Nageli has been used in research for the removal of nitrogen and organic matter in order to associate single-cell protein production with wastewater treatment. These micro-organisms use photosynthesis as the main metabolic way, although some strains are able to grow in absence of light in heterotrophic cultures. Therefore, the main purpose of the work was to evaluate the growth kinetics of unicellular cyanobacterium A. microscopica in rice parboilization effluent without light source. Experimental conditions were 100 and 300u2009mgu2009L−1 inoculum concentration at 25 and 35°C. Results showed that biomass production with maximum nitrogen and organic matter removal at 12u2009h of batch time was 300u2009mgu2009L−1 inoculum at 35°C. Our results demonstrate that A. microscopica shows high yield of nitrogen and organic matter removal from rice parboilization effluent, promising of potential for biomass products and wastewater treatment.

Catechol biodegradation kinetics using Candida parapsilopsis.

This study evaluated the biodegradation of catechol by a yeast strain of Candida parapsilopsis in standard medium in Erlenmeyer flasks. Results shown that the highest concentration of catechol caused the longer lag period, demonstrating that acclimatized cultures could completely degrade an initial catechol concentration of 910 mg/L within 48 h. Haldanes model validated the experimental data adequately for growth kinetics over the studied catechol concentration ranges of 36 to 910 mg/L. The constants obtained for this model were µmax = 0.246 h-1, Ks = 16.95 mg/L and Ki = 604.85 mg/L.

Effects of feedstock and co-culture of Lactobacillus fermentum and wild Saccharomyces cerevisiae strain during fuel ethanol fermentation by the industrial yeast strain PE-2

Even though contamination by bacteria and wild yeasts are frequently observed during fuel ethanol fermentation, our knowledge regarding the effects of both contaminants together is very limited, especially considering that the must composition can vary from exclusively sugarcane juice to a mixture of molasses and juice, affecting the microbial development. Here we studied the effects of the feedstock (sugarcane juice and molasses) and the co-culture of Lactobacillus fermentum and a wild Saccharomyces cerevisiae strain (rough colony and pseudohyphae) in single and multiple-batch fermentation trials with an industrial strain of S. cerevisiae (PE-2) as starter yeast. The results indicate that in multiple-cycle batch system, the feedstock had a minor impact on the fermentation than in single-cycle batch system, however the rough yeast contamination was more harmful than the bacterial contamination in multiple-cycle batch fermentation. The inoculation of both contaminants did not potentiate the detrimental effect in any substrate. The residual sugar concentration in the fermented broth had a higher concentration of fructose than glucose for all fermentations, but in the presence of the rough yeast, the discrepancy between fructose and glucose concentrations were markedly higher, especially in molasses. The biggest problem associated with incomplete fermentation seemed to be the lower consumption rate of sugar and the reduced fructose preference of the rough yeast rather than the lower invertase activity. Lower ethanol production, acetate production and higher residual sugar concentration are characteristics strongly associated with the rough yeast strain and they were not potentiated with the inoculation of L. fermentum.

Single and combined effects of acetic acid, furfural, and sugars on the growth of the pentose-fermenting yeast Meyerozyma guilliermondii

The tolerance of the pentose-fermenting yeast Meyerozyma guilliermondii to the inhibitors released after the biomass hydrolysis, such as acetic acid and furfural, was surveyed. We first verified the effects of acetic acid and cell concentrations and initial pH on the growth of a M. guilliermondii strain in a semi-synthetic medium containing acetic acid as the sole carbon source. Second, the single and combined effects of furfural, acetic acid, and sugars (xylose, arabinose, and glucose) on the sugar uptake, cell growth, and ethanol production were also analysed. Growth inhibition occurred in concentrations higher than 10.5xa0gxa0l−1 acetic acid and initial pH 3.5. The maximum specific growth rate (µ) was 0.023xa0h−1 and the saturation constant (ks) was 0.75xa0gxa0l−1 acetic acid. Initial cell concentration also influenced µ. Acetic acid (initial concentration 5xa0gxa0l−1) was co-consumed with sugars even in the presence of 20xa0mgxa0l−1 furfural without inhibition to the yeast growth. The yeast grew and fermented sugars in a sugar-based medium with acetic acid and furfural in concentrations much higher than those usually found in hemicellulosic hydrolysates.

Biofuels from Microalgae: Bioethanol

The industrial potential of ethanol has been tested early in 1800 to be used as an engine fuel after the invention of an internal combustion engine. Currently, there are three generations of bioethanol that have been flourished based on different feedstocks. The first-generation bioethanol is derived from fermentation of glucose contained in starch and/or sugar crops. USA and Brazil are the main producers of bioethanol worldwide utilizing corn and sugarcane, while potato, wheat, and sugar beet are the common feedstocks for bioethanol in Europe. The term “second-generation bioethanol” emerged as a boon to overcome the “food versus fuel” that occurs by the first-generation bioethanol. The second generation also referred to as “advanced biofuels” is produced by innovative processes mainly using lignocellulosic feedstock and agricultural forest residues. The emergence of the third-generation bioethanol provides more benefits as compared to the first and second generations and is focused on the use of microalgae and cyanobacteria. These organisms represent as a promising alternative feedstock due to its high lipid and carbohydrate contents, easy cultivation in a wide variety of water environment, relatively low land usage and carbon dioxide absorption. This chapter will discuss the use of microalgae for the ethanol production and the main technological routes, i.e., enzymatic hydrolysis and yeast fermentation of microalgal biomass, metabolic pathways in dark conditions, and “photofermentation.”

Yeast for Pentose Fermentation: Isolation, Screening, Performance, Manipulation, and Prospects

The global demand for energy has led the research and the investments to use plant biomass to convert the sugars contained in this material into ethanol. The characteristics of the substrate and process have a strong impact on the choice of microorganisms to be used for fermentation of the sugars. In the most of feedstocks for ethanol production, the sugars containing five carbons (pentoses) are abundant. Naturally occurring yeasts that can use pentoses as carbon source have been isolated from the environment, and among them, Pichia stipitis is one of the most important species. However, some important characteristics needed in ethanol industry are high resistance to inhibiting compounds and high fermentation performance and, until this moment, none a single strain that gather these features has not been found naturally. Techniques of evolutionary engineering and genetic manipulation have been applied to introduce and select the required traits for pentose fermentation in Saccharomyces cerevisiae, the most employed yeast industrially. This chapter discusses the context of the microorganisms, especially the yeast group, in the fermentation of hemicellulosic substrates for bioethanol production regarding isolation, screening, performance, limitations, prospects, and state of the art, trying to contribute to the improvement of the global process of ethanol production.