Fruit residues as biomass for bioethanol production using enzymatic hydrolysis as pretreatment.

The commercialization of fruits in markets generates a large amount of waste because they are perishable and have a short shelf life, so, they are discarded. This study aimed to provide a noble end to discarded fruits that have fermentable sugars. Banana, apple, mango and papaya residues were collected from supermarkets and underwent an enzymatic hydrolysis process. The ability of four pectinases, two amylases, one xylanase and one cellulase to release reducing sugars from fruit biomass before fermentation with two yeast strains (S. cerevisiae CAT-1 and S. cerevisiae Angel) for bioethanol production was investigated, obtaining a total of RS (Reducing sugar) of 268.08 mg/mL in banana residues. A fermentation with yeast S. cerevisiae CAT-1 resulted in 98% consumption of RS and the production of a total of 28.02 g/L of ethanol. Furthermore, fermentation with the yeast S. cerevisiae Angel, resulted in 97% RS consumption and 31.87 g/L ethanol production, which was the best result obtained throughout all the tests of hydrolysis, highlighting the banana residue as a promising biomass for the production of bioethanol.

Rhodococcus: A promising genus of actinomycetes for the bioremediation of organic and inorganic contaminants.

Rhodococcus is a genus of actinomycetes that has been explored by the scientific community for different purposes, especially for bioremediation uses. However, the mechanisms governing Rhodococcus-mediated bioremediation processes are far from being fully elucidated. In this sense, this work aimed to compile the recent advances in the use of Rhodococcus for the bioremediation of organic and inorganic contaminants present in different environmental compartments. We reviewed the bioremediation capacity and mechanisms of Rhodococcus spp. in the treatment of polycyclic aromatic hydrocarbons, phenolic substances, emerging contaminants, heavy metals, and dyes given their human health risks and environmental concern. Different bioremediation techniques were discussed, including experimental conditions, treatment efficiencies, mechanisms, and degradation pathways. The use of Rhodococcus strains in the bioremediation of several compounds is a promising approach due to their features, primarily the presence of appropriate enzyme systems, which result in high decontamination efficiencies; but that vary according to experimental conditions. Besides, the genus Rhodococcus contains a small number of opportunistic species and pathogens, representing an advantage from the point of view of safety. Advances in analytical detection techniques and Molecular Biology have been collaborating to improve the understanding of the mechanisms and pathways involved in bioremediation processes. In the context of using Rhodococcus spp. as bioremediation agents, there is a need for more studies that 1) evaluate the role of these actinomycetes on a pilot and field scale; 2) use genetic engineering tools and consortia with other microorganisms to improve the bioremediation efficiency; and 3) isolate new Rhodococcus strains from environments with extreme and/or contaminated conditions aiming to explore their adaptive capabilities for bioremediation purposes.

Bacterial biosurfactant increases ex situ biodiesel bioremediation in clayey soil.

The contamination of soils by oily compounds has several environmental impacts, which can be reversed through bioremediation, using biosurfactants as auxiliaries in the biodegradation process. In this study, we aimed to perform ex situ bioremediation of biodiesel-contaminated soil using biosurfactants produced by Bacillus methylotrophicus. A crude biosurfactant was produced in a whey-based culture medium supplemented with nutrients and was later added to biodiesel-contaminated clayey soil. The produced lipopeptide biosurfactant could reduce the surface tension of the fermentation broth to 30.2 mN/m. An increase in the microbial population was observed in the contaminated soil; this finding can be corroborated by the finding of increased CO2 release over days of bioremediation. Compared with natural attenuation, the addition of a lower concentration of the biosurfactant (0.5% w/w in relation to the mass of diesel oil) to the soil increased biodiesel removal by about 16% after 90 days. The added biosurfactant did not affect the retention of the contaminant in the soil, which is an important factor to be considered when applying in situ bioremediation technologies.

Improving the Bioremediation and in situ Production of Biocompounds of a Biodiesel-Contaminated Soil.

We aimed to produce simultaneously biosurfactants and lipases in solid state fermentation (SSF) using Aspergillus niger, followed by the use of the fermented media on the bioremediation of oily contaminated soil, in order to valuate agro industrial residuals and reduce the contamination. The biocompounds were produced using wheat bran and corncob (80:20), 5% of soybean oil and 0.5% of sugar cane molasses in SSF for 4 d, producing 4.58 ± 0.69 UE of emulsifying activity and 7.77 ± 1.52 U of lipolytic activity. This fermented media was used in the bioremediation of a 20% biodiesel contaminated soil, evaluating for 90 d microbial growth, contaminant degradation, and production of lipases and biosurfactants in soils. Six experimental strategies (natural attenuation; biostimulation + bioaugmentation + biocompounds; biostimulation + biosurfactant; biocompounds extract; biostimulation; adsorption of contaminant) were realized. The highest degradation of contaminant was verified in 90 d, of 74.40 ± 1.76%, and the production of biosurfactants and lipases in situ in the soil was found in 30 d (6.02 ± 0.24% of reduction in surface tension and 6.62 ± 0.17 UL of lipid activity in soil) for the same experiment (biostimulation + bioaugmentation + biocompounds). The addition of biostimulation + biosurfactant promotes higher biodegradation (66.00 ± 0.92%) of the contaminant than the biocompounds extract (59.58 ± 0.34%). The use of a solid fermented culture medium containing both biocompounds was feasible for the treatment of contaminants, demonstrating the potential for environmental application without the need for purification processes.

Effects of homemade biosurfactant from Bacillus methylotrophicus on bioremediation efficiency of a clay soil contaminated with diesel oil.

Despite constant progress in the understanding of the mechanisms related to the effects of biosurfactants in the bioremediation processes of oily residues, the possibility of antagonist effects on microbial growth and the production in situ of these compounds must be elucidated. The aims of this work were a) to evaluate the effects of the addition of a homemade biosurfactant of Bacillus methylotrophicus on the microbial count in soil in order to determine the possibility of inhibitory effects, and b) to accomplish biostimulation using media prepared with whey and bioaugmentation with B. methylotrophicus, analyzing the effects on the bioremediation of diesel oil and evidencing the in situ production of biosurfactants through effects on surface tension. The homemade bacterial biosurfactant did not present inhibitory effects acting as a biostimulant until 4000 mg biosurfactant/kg of soil. The biostimulation and bioaugmentation presented similar better results (p > 0.05) with the degradation of oil (~60%) than natural attenuation due to the low quantities of biostimulants added. For bioaugmentated and biostimulated soils, a decrease of surface tension between 30 and 60 days was observed, indicating the production of tensoactives in the soil, which was not observed in natural attenuation or a control treatment.

Development of functional pasta with microencapsulated Spirulina: technological and sensorial effects.

BACKGROUND: Spirulina microalgae have been added to food; however, there have been few reports on the methods used to protect the antioxidant potential against process conditions, and the effects on the sensory characteristics of products need to be better described. The aim of this study was to evaluate the influence on the technological properties, sensory profile, and acceptability of the pasta with free or microencapsulated Spirulina biomass added. Pasta formulations included: free Spirulina (FSP), microencapsulated Spirulina (MSP), and empty microspheres (EMP), which were compared with the control pasta (CP). RESULTS: The microencapsulation protected the antioxidant potential of Spirulina in 37.8% of the pasta cooking conditions. The microspheres presented low solubility in water (86 g.kg-1 ) and high encapsulation efficiency (87.6%), this being appropriate for addition to products that need cooking in water. The technological properties of pasta (water absorption, weight gain, firmness, and adhesiveness) were affected, but the overall acceptability index (85.13%) was not influenced by the addition of microspheres, despite changes observed in the sensory profile obtained by the CATA (check-all-that-apply). CONCLUSIONS: Spirulina could be added to pasta even without microencapsulation but the microencapsulation in alginate allows for the protection of the antioxidant potential of the biomass, representing a potential alternative for the bakery industry. © 2019 Society of Chemical Industry.

Successive membrane separation processes simplify concentration of lipases produced by Aspergillus niger by solid-state fermentation.

In this study, we developed a simplified method for producing, separating, and concentrating lipases derived from solid-state fermentation of agro-industrial residues by filamentous fungi. First, we used Aspergillus niger to produce lipases with hydrolytic activity. We analyzed the separation and concentration of enzymes using membrane separation processes. The sequential use of microfiltration and ultrafiltration processes made it possible to obtain concentrates with enzymatic activities much higher than those in the initial extract. The permeate flux was higher than 60 L/m2 h during microfiltration using 20- and 0.45-µm membranes and during ultrafiltration using 100- and 50-kDa membranes, where fouling was reversible during the filtration steps, thereby indicating that the fouling may be removed by cleaning processes. These results demonstrate the feasibility of lipase production using A. niger by solid-state fermentation of agro-industrial residues, followed by successive tangential filtration with membranes, which simplify the separation and concentration steps that are typically required in downstream processes.

Potential application of microalga Spirulina platensis as a protein source.

The high protein level of various microalgal species is one of the main reasons to consider them an unconventional source of this compound. Spirulina platensis stands out for being one of the richest protein sources of microbial origin (460-630 g kg-1 , dry matter basis), having similar protein levels when compared to meat and soybeans. The use of S. platensis in food can bring benefits to human health owing to its chemical composition, since it has high levels of vitamins, minerals, phenolics, essential fatty acids, amino acids and pigments. Furthermore, the development of new protein sources to supply the shortage of this nutrient is an urgent need, and protein from S. platensis plays an important role in this scenario. In this sense, extraction processes that allow maximum protein yield and total utilization of biomass is an urgent need, and ultrasonic waves have proven to be an effective extraction technique. The number of scientific papers related to protein fraction from S. platensis is still limited; thus further studies on its functional and technological properties are needed. © 2016 Society of Chemical Industry.

Potential of Live Spirulina platensis on Biosorption of Hexavalent Chromium and Its Conversion to Trivalent Chromium.

Microalga biomass has been described worldwide according their capacity to realize biosorption of toxic metals. Chromium is one of the most toxic metals that could contaminate superficial and underground water. Considering the importance of Spirulina biomass in production of supplements for humans and for animal feed we assessed the biosorption of hexavalent chromium by living Spirulina platensis and its capacity to convert hexavalent chromium to trivalent chromium, less toxic, through its metabolism during growth. The active biomass was grown in Zarrouk medium diluted to 50% with distilled water, keeping the experiments under controlled conditions of aeration, temperature of 30°C and lighting of 1,800 lux. Hexavalent chromium was added using a potassium dichromate solution in fed-batch mode with the aim of evaluate the effect of several additions contaminant in the kinetic parameters of the culture. Cell growth was affected by the presence of chromium added at the beginning of cultures, and the best growth rates were obtained at lower metal concentrations in the medium. The biomass removed until 65.2% of hexavalent chromium added to the media, being 90.4% converted into trivalent chromium in the media and 9.6% retained in the biomass as trivalent chromium (0.931 mg.g(-1)).

Co-production of lipases and biosurfactants by Bacillus methylotrophicus in solid-state fermentation.

The production of biosurfactants and lipases through solid-state fermentation (SSF) processes remains relatively unexplored, especially in bacterial applications. The use of solid matrices, eliminating the need for precipitation and recovery processes, holds significant potential for facilitating bioremediation. This study aimed to simultaneously produce biocompounds via SSF using Bacillus methylotrophicus and employ the fermented substrate for remediating soil contaminated with 20% biodiesel. Initial efforts focused on determining optimal conditions for concurrent lipase and biosurfactant production during an 8-day fermentation period. The selected conditions, including a substrate mix of wheat bran and corn cob (80/20), 75% moisture, 1% glycerol inducer, 2% nitrogen, and 1% sugarcane molasses, resulted in a 24.61% reduction in surface tension and lipase activity of 3.54 ± 1.20 U. Subsequently, a 90-day bioremediation of clayey soil contaminated with biodiesel showcased notable biodegradation, reaching 72.08 ± 0.36% within the initial 60 days. The incorporation of biocompounds, biostimulation, and bioaugmentation (Test E2) contributed to this efficacy. The use of the fermented substrate as a biostimulant and bioaugmentation agent facilitated in situ biocompound production in the soil, leading to a 23.97% reduction in surface tension and lipase production of 1.52 ± 0.19 U. Supplementary Information: The online version contains supplementary material available at 10.1007/s13205-023-03910-7.

Biochar-immobilized Bacillus spp. for heavy metals bioremediation: A review on immobilization techniques, bioremediation mechanisms and effects on soil.

Heavy metals contamination present risks to ecosystems and human health. Bioremediation is a technology that has been applied to minimize the levels of heavy metals contamination. However, the efficiency of this process varies according to several biotic and abiotic aspects, especially in environments with high concentrations of heavy metals. Therefore, microorganisms immobilization in different materials, such as biochar, emerges as an alternative to alleviate the stress that heavy metals have on microorganisms and thus improve the bioremediation efficiency. In this context, this review aimed to compile recent advances in the use of biochar as a carrier of bacteria, specifically Bacillus spp., with subsequent application for the bioremediation of soil contaminated with heavy metals. We present three different techniques to immobilize Bacillus spp. on biochar. Bacillus strains are capable of reducing the toxicity and bioavailability of metals, while biochar is a material that serves as a shelter for microorganisms and also contributes to bioremediation through the adsorption of contaminants. Thus, there is a synergistic effect between Bacillus spp. and biochar for the heavy metals bioremediation. Biomineralization, biosorption, bioreduction, bioaccumulation and adsorption are the mechanisms involved in this process. The application of biochar-immobilized Bacillus strains results in beneficial effects on the contaminated soil, such as the reduction of toxicity and accumulation of metals in plants, favoring their growth, in addition to increasing microbial and enzymatic activity in soil. However, competition and reduction of microbial diversity and the toxic characteristics of biochar are reported as negative impacts of this strategy. More studies using this emerging technology are essential to improve its efficiency, to elucidate the mechanisms and to balance positive and negative impacts, especially at the field scale.

Use of soil actinomycetes for pharmaceutical, food, agricultural, and environmental purposes.

In this article, we reviewed the international scientific production of the last years on actinomycetes isolated from soil aiming to report recent advances in using these microorganisms for different applications. The most promising genera, isolation conditions and procedures, pH, temperature, and NaCl tolerance of these bacteria were reported. Based on the content analysis of the articles, most studies have focused on the isolation and taxonomic description of new species of actinomycetes. Regarding the applications, the antimicrobial potential (antibacterial and antifungal) prevailed among the articles, followed by the production of enzymes (cellulases and chitinases, etc.), agricultural uses (plant growth promotion and phytopathogen control), bioremediation (organic and inorganic contaminants), among others. Furthermore, a wide range of growth capacity was verified, including temperatures from 4 to 60 °C (optimum: 28 °C), pH from 3 to 13 (optimum: 7), and NaCl tolerance up to 32% (optimum: 0-1%), which evidence a great tolerance for actinomycetes cultivation. Streptomyces was the genus with the highest incidence among the soil actinomycetes and the most exploited for different uses. Besides, the interest in isolating actinomycetes from soils in extreme environments (Antarctica and deserts, for example) is growing to explore the adaptive capacities of new strains and the secondary metabolites produced by these microorganisms for different industrial interests, especially for pharmaceutical, food, agricultural, and environmental purposes.

Fruit extract of red pitaya (Hylocereus undatus) prevents and reverses stress-induced impairments in the cholinergic and antioxidant systems of Caenorhabditis elegans.

The addition of fruit to the diet is very important, and we can use nutraceutical and functional foods for this supplement. A little-known fruit is a red pitaya (Hylocereus undatus) that has been widely reported to have a high antioxidant potential. In this study, we analyzed the in vitro and in vivo antioxidant capacity of microencapsulated pitaya extract on the behavior, antioxidant, and nervous system of the nematode Caenorhabditis elegans. The worms were treated with fruit extract before and after juglone-induced stress, to determine the protective or curative effects of pitaya. We have been evaluated cholinergic, antioxidant, and behavioral biomarkers. We have evidenced that the pulp of pitaya contains antioxidant compounds and can serve as a potential nutraceutical product. In addition, the fruit extract was effective in preventing and/or reverse the stress-induced damages, even at high levels of chemical stress at all evaluated parameters. PRACTICAL APPLICATIONS: The potential applications and uses aimed by this research are related to the supplementation of foods given the antioxidant effect. Our data suggested that the effect of the pitaya fruit microencapsulated pulp extract was effective to prevent and repair the damage caused by oxidative stress. Besides the use of this microencapsulated extract can be an auxiliary in the treatment of diseases related to oxidative damage as well as promoting senescent aging. Another important use is the application of this extract as a dietary supplement to fortify the antioxidant system.

Harvesting of Spirulina platensis using an eco-friendly fungal bioflocculant produced from agro-industrial by-products.

This study aimed to produce fungal biomass from agro-industrial by-products for later use as a bioflocculant in the Spirulina harvesting. The production of fungal biomass from Aspergillus niger was carried out in submerged fermentation, using media composed of wheat bran and/or potato peel. Fungal biomass was used as a bioflocculant in Spirulina cultures carried out in closed 5 L reactors and 180 L open raceway pond operated in batch and semi-continuous processes, respectively. Fungal biomass was able to harvest Spirulina platensis cultures with efficiencies between 90% and 100% after 2 h of sedimentation in some experimental conditions. Efficiencies higher than 80% were achieved in most tests without pH adjustment during bioflocculations, which shows that the developed method is a promising alternative to traditional Spirulina harvesting techniques. Above all, the development of an eco-friendly fungal-assisted bioflocculation process increases the sustainability of Spirulina biomass for different applications, especially biofuels.

Current advances in microalgae-based bioremediation and other technologies for emerging contaminants treatment.

Emerging contaminants (EC) have been detected in effluents and drinking water in concentrations that can harm to a variety of organisms. Therefore, several technologies are developed to treat these compounds, either for their complete removal or degradation in less toxic by-products. Some technologies applied to the treatment of EC, such as adsorption, advanced oxidative processes, membrane separation processes, and bioremediation through microalgal metabolism, were identified by thematic maps. In this review, we used a bibliometric software from >1000 articles. These manuscripts, in general, present removals from 0% to 100% for different ECs. This efficiency varies between treatment technologies and the contaminants' physical-chemical properties and their concentration and operational parameters. This review explored the bioremediation of EC through microalgae with greater emphasis. The main mechanisms of action of microalgae in the bioremediation of ECs are biodegradation bioadsorption, and bioaccumulation. Also, physicochemical properties and removal efficiencies of >50 emerging contaminants are presented. Although there are challenges related to the generation of more toxic by-products and economic and environmental viability, these can be minimized with advances in the development of treatment technologies and even through the integration of different techniques to make the treatment of contaminants emerging from environmental media more sustainable.

Selection of lipase-producing microorganisms through submerged fermentation.

Lipases are enzymes used in various industrial sectors such as food, pharmaceutical and chemical synthesis industries. The selection of microorganisms isolated from soil or wastewater is an alternative to the discovery of new species with high enzymes productivity and with different catalytic activities. In this study, the selection of lipolytic fungi was carried out by submerged fermentation. A total of 27 fungi were used, of which 20 were isolated from dairy effluent and 7 from soil contaminated with diesel oil. The largest producers were the fungi Penicillium E-3 with maximum lipolytic activity of 2.81 U, Trichoderma E-19 and Aspergillus O-8 with maximum activities of 2.34 and 2.03 U where U is the amount of enzyme that releases 1 micromol of fatty acid per min per mL of enzyme extract. The fungi had maximum lipolytic activities on the 4th day of fermentation.

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.

Simultaneous saccharification and fermentation of Spirulina sp. and corn starch for the production of bioethanol and obtaining biopeptides with high antioxidant activity.

The aim was to produce bioethanol by the simultaneous saccharification and fermentation (SSF) of Spirulina sp. LEB 18 biomass and corn starch, increasing the process scale and obtaining biopeptides from bioethanol residue. Different temperatures of SSF and biomass/starch concentrations were tested, and the best conditions were chosen to scale-up the bioethanol production. The biopeptides were obtained enzymatically with a protease. The antioxidant capacity, molecular structure, thermal stability and mass loss of the biopeptides were evaluated. A total of 73 g L-1 bioethanol was obtained during scale-up, and the residue presented a high protein content with a degree of hydrolysis of 86%. The biopeptides showed 32% ABTS radical inhibition with high thermal stability. This study showed the possibility of the biorefinery concept being able to produce bioethanol by Spirulina, and the biopeptides from the bioethanol residue presented high antioxidant capacity and can be used in many areas of the food industry.

Effects of harvesting Spirulina platensis biomass using coagulants and electrocoagulation-flotation on enzymatic hydrolysis.

This study aimed to assess the harvesting of Spirulina platensis using coagulants and electrocoagulation-flotation (ECF) and to evaluate its influence on enzymatic hydrolysis. Using nine chemical coagulants, we obtained a biomass harvesting efficiency of up to 99.5%. Using ECF, the harvesting efficiency at the aluminum and carbon electrode was 98%-99% and 33.8%-86.9%, respectively. Hydrolysis efficiency (HE) with amylases varied from 17% to 42%, and the degree of hydrolysis (DH) with proteases varied from 1.26% to 4.07%, compared with an HE of 31% and a DH of 3.57% in the centrifuged biomass. Compared to an HE of 61.75% for the centrifuged biomass, and HE of 99% and 85.46% was obtained for the biomass harvested using the aluminum and carbon electrodes. The HEs with the electrodes were better than those with the alternative methods and centrifugation; hence, with some optimization, the biomass harvested could be used for enzymatic hydrolysis.

A solid-state bioprocess for selecting lipase-producing filamentous fungi.

A solid-state bioprocess with wheat bran and rice husk as substrate was used to isolate filamentous fungi with lipase activity from dairy effluent and soil contaminated with diesel oil. The lipase activity was measured in units, with one unit (U) being defined as the amount of enzyme required to liberate 1 micromol of fatty acids per minute per gram of bran substrate (1 U = 1 micromol min(-1) g(-1)). We obtained 24 isolates of filamentous fungi with lipase activity, 17 from the dairy effluent and 7 from the diesel oil-contaminated soil. The best lipase producers were the dairy effluent isolate Aspergillus E-6, with a maximum lipase activity of 49.81 U, and Aspergillus isolate O-4 recovered from the diesel oil-contaminated soil, with a maximum lipase activity of 45.49 U. Both isolates produced their maximum lipase activity eight days after the start of the bioprocess.