Industrial Biotechnology

The use of agricultural residues in products of commercial interest plays an increasingly important role in the world, which has a growing source of income in agribusiness. The current study investigates the potential use of rice husk ash (RHA) produced using different biomass combustion techniques as an alternative source of silica for the synthesis of LTA zeolites. RHA used in this work did not undergo any previous treatments and the zeolite synthesis was performed on the absence of an organic structure directing agent. Rice husk was submitted to three different burning processes: grate, fluidized bed, and under controlled laboratory conditions. Zeolite LTA was prepared via direct dissolution of the RHA. The obtained zeolite material was characterized crystallographic and morphological. LTA framework structure was successfully obtained using all types of RHA.

The waste generated by cassava starch processing has an ample variety of molecules that can be converted to value-added products. Cassava starch wastewater (CSW) has a high nutritional value and can be used as a substrate in biological processes, in addition to providing microorganisms of biotechnological interest, due to the rich native biota present. Bacteriocins—peptides synthesized by ribosomes—are capable of inactivating or inhibiting the growth of pathogenic bacteria, used to preserve food, and can be isolated from CSW. This study evaluated growth conditions to produce bacteriocins from a lactic acid bacterium Leuconostoc mesenteroides isolated from CSW, using residues from the cassava processing agroindustry as substrate. The experimental planning by Plackett & Burman (PB) was carried out to evaluate the effects of the variable's sucrose, yeast extract, potassium phosphate, magnesium sulfate, and Tween 80, with 15 assays, 36 h of incubation, and agitation at 100 rpm. From these assays, it was verified that only the variables sucrose, yeast extract, and tween 80 were significant at 90%. The results indicated a maximum bacteriocin production of 1990.47 AU/mL (assay 14), COD (chemical oxygen demand) removal efficiency of 59.99% (assay 11), the sugar removal efficiency of 55.89 (assay 14), and production of lactic acid 21.41 g/L (assay 6).

Brazil has made significant progress in ethanol production from sugarcane juice. However, in terms of water, food, and environmental safety, this production can be optimized by replacing raw food with agricultural waste, giving rise to second-generation ethanol (2G). Among these biomasses, coconut residue stands out in tropical countries like Brazil. This study aimed to fractionate coconut husk through alkaline pretreatment with calcium hydroxide (20% w/w) followed by enzymatic hydrolysis with Novozymes^TM Ctec2 and Htec2. The conversion efficiency of polysaccharides into monosaccharides was 19.3% for cellulose and 7.3% for hemicellulose. The inhibitors acetic acid (∼3.0 g/L) and formic acid (∼0.8 g/L) were also observed in the hydrolysate, to which 17.5 g/L NaCl was added to evaluate yeast cells under salt stress. The wild strain Wickerhamomyces sp. UFFS-CE-3.1.2 and the industrial yeast Saccharomyces cerevisiae PE-2 were inoculated into this non-detoxified high-salt hydrolysate and analyzed through a Central Composite Design (CCD). The independent variables were the effects of pH and temperature on yeast metabolism. Assuming cellular growth and sugar consumption as responses to the experimental design, pH of 7.0 and temperature of 40°C were defined as the best cultivation conditions for subsequent fermentation kinetics. As a result, the wild yeast showed the highest biomass production, but it did not produce ethanol. In contrast, the industrial strain fermented glucose, displaying an ethanol yield of 0.24 g_ethanol/g_sugar. Thus, coconut husk can be promising biomass for 2G ethanol production, even though it requires pretreatment and hydrolysis optimization to increase sugar concentration and reduce inhibitors in the hydrolysate.

Non-timber forest products originating from native Brazilian trees, such as Araucaria angustifolia (Bertol.), stand out within the scope of the global concept of bioeconomy. The pine fruit from A. angustifolia, known in Portuguese as pinhão, is an edible seed covered with a coat that is considered as solid waste. The aim of this study was to investigate the drying kinetics of the pinhão coats and seeds to obtain and characterize two types of flour. The drying temperature (70°C) and air velocity (1.0 ms-¹) were the parameters used to obtain the drying curves. These curves were fitted using five empirical and semiempirical mathematical models to establish predictive equations for the drying process. After drying, the coats and the seed were ground (30-mesh sieve) separately to obtain two types of flour samples, which were nutritionally characterized and their antioxidant activity was quantified. The equilibrium moisture values were 2.90% for the coats and 1.71% for the seeds. The Page and the Overhults models provided the best results for both coats and seeds (R² = 0.9996; χ2 = 0.1926 and R² = 0.9971; χ2 = 0.3702, respectively). The nutritional composition results for the coat flour indicated high values for dietary fiber (84.91%), phenolic compounds (39.53 mg_EC g⁻¹) and DPPH radical scavenging activity (93.23%), while the seed flour showed a high content of total carbohydrates (80.07%). Thus, the use of these products obtained from pinhão coats and seeds as a food ingredient is a promising strategy to promoting environmental sustainability and bioeconomy, while also enhancing human health.

Lignocellulosic waste was transformed into high-added value materials, hydrochars, through hydrothermal carbonization. The influence of temperature and residence time on the properties of the hydrochars derived from rice husk and exhausted black wattle bark was evaluated. Hydrothermal carbonization enhanced carbon content in the solid material by more than 30% in both materials. As temperature and residence time increased, however, process yield decreased between 3 and 27%. Porosity was created in the solid material during hydrothermal carbonization; a specific surface area value of 45 m² g⁻¹ was attained. The presence of oxygenated functional groups and aromatic rings was also evidenced by the carbonization treatment. Thus, hydrothermal carbonization of rice husk and exhausted black wattle bark was efficient for improving carbon content, porosity, and functionality in the solid material.

CEASAs (wholesaler food supply centers) are strategically located throughout the Brazilian territory. However, food circulation leads to a high generation of fruit and vegetable waste. CEASA-Maracanaú (Ceará state, Brazil) is an example of this, sending around 17 tons of organic waste to the landfill each day without categorization. An environmentally friendly option to reuse fruit and vegetable wasted (FVW) at CEASA-Maracanaú is using it as a substrate in methane production through anaerobic digestion, which requires a detailed quality and quantity characterization. This study aimed to characterize the FVW generated at CEASA-Maracanaú to evaluate its biomethane potential and estimate energy recovery. To characterize the residue, questionnaires were sent to 1,200 permit holders. The results pointed to a residue composed of orange (42.0%), onion (7.7%), corn (5.5%), papaya (5.4%), avocado (4.8%), watermelon (3.4%), banana (3.0%), melon (3.1%), potato (3.0%), pineapple (3.1%), cabbage (2.4%), guava (1.2%), and tomato (1.0%), among others. This composition was crushed and characterized in terms of chemical oxygen demand (138.13 ± 12.4 gCOD/kgFVW). Biomethane potential tests of crushed residue was 275 NmL_CH4/gCOD or 313 NmL_CH4/gVS, resulting in 79.3% biodegradability. From this potential, it is estimated that FVW from CEASA-Maracanaú yields a methane-based energy recovery of up to 373 KW of thermic power. As a result, it is possible to meet 86% energy demand of CEASA-Maracanaú during the rush-hour (5:30 pm to 8:30 pm) rate by employing the energy recovered from the daily accumulated biogas.

The application of maximum feedstock capacity through the treatment of organic wastes generated in the industrial chain is necessary for environmental preservation. Agro-industrial waste, such as from fruit processing, can be treated by anaerobic digestion with bioenergy generation. This study aimed to evaluate the consumption of guava processing waste on hydrogen (H₂) and methane (CH₄) production in a two-stage anaerobic system under four different conditions (substrate/inoculum ratios of 0.67, 1.0, 2.0, and 3.0 g COD g⁻¹ VS). Bio-H₂ (5.26–3.50 mL H₂ g⁻¹ VS) and bio-CH₄ (266.27–104.67 mL CH₄ g⁻¹ VS) were produced, with consequent high efficiencies of organic matter (75–90% to total COD) and carbohydrates (98–99%) removals. Paraclostridium and Clostridium genera were used in ethanol, acetic, propionic, and butyric acids generation in the first stage, and these metabolites were consumed in the second stage. The estimated energy yields of the two-stage system were 1.1–2.7 kJ kg⁻¹ residue. Guava residues can be recovered by application in anaerobic processes for the generation of biofuels and other added-value bioproducts.

Global biodiesel production has increased, and 10 kg of crude glycerol (CG) is being generated as a coproduct for each 100 kg of biodiesel produced. Brazil is the main citrus-producing country in the world, generating highly fermentable carbohydrates that are used for the second-generation ethanol production with citrus vinasse (CV) as waste product. The goal of this study was to evaluate the use of CG, the coproduct from transesterification of waste cooking oil, co-digested in CV through a biosystem in two-sequential stages: the first one acidogenic for lactic acid generation and the second one methanogenic for CH₄ production. For the first stage, with an acid pre-treated consortium, the maximum lactic acid generated was 2.31 g L⁻¹ in anaerobic batch reactors (500 mL) containing 400 mL of medium composed of 10 g COD L⁻¹ CG with 10 g COD L⁻¹ CV, pH 6.0, headspace with N₂, at 37°C. The liquid fraction generated in the first stage (200 mL) was used as substrate by an anaerobic consortium in natura in anaerobic methanogenic reactors (500 mL), headspace with N₂, pH 7.0, at 37°C, generating a maximum of 318.65 mmol CH₄ L⁻¹ in 815 h of operation. In addition, 85.65% of the COD was removed and all methanol from the CG was consumed. Integrated systems correspond to major measures for the removal of CG in obtaining value-added products such as lactic acid, in addition to the generation of biogas as CH₄.

Anaerobic digestion (AD) is a technology that allows waste management. For this process to be carried out correctly, an appropriate inoculum is required to degrade organic matter to produce biogas and digestate. However, in rural areas of developing countries, an inoculum from an anaerobic treatment plant is not available. In addition, various agricultural and agro-industrial wastes are generated in these areas, but there are also low-cost digesters that operate mainly with cattle manure. Therefore, this study aimed to determine the energy potential of agro-industrial waste using cattle slurry as inoculum in the AD. The substrates used were sugarcane residues, cheese whey, and slaughterhouse wastewater. Biochemical methane potential (BMP) tests were conducted in 500 mL glass flasks at 35 ± 2°C, ISR of 2, and volume displacement measured methane production. Organic matter removal (based on volatile solids) and buffer capacity (VFA/TA ratio) were determined. Sugarcane residues showed a BMP ranging between 0.21–0.28 Nm³CH₄/kgVS_ad, cheese whey between 0.42–0.60 Nm³CH₄/kgVS_ad, and slaughterhouse wastewater 0.15–0.50 Nm³CH₄/kgVS_ad. For the three cases, buffer capacity was <0.35 mg eq acetic acid/mg CaCOO₃, evidencing low inhibition risks and removing greater than 70% of organic matter. Cattle slurry was suitable as an inoculum for the AD of agro-industrial and agricultural residues, which could boost the bioeconomy of rural areas in developing countries.