RESUMO
The statistical experimental design (DoE) and optimization (Response Surface Methodology combined with Box-Behnken design) of sunflower oil transesterification catalyzed by waste chicken eggshell-based catalyst were conducted in a custom-made microreactor at 60 °C. The catalyst was synthesized by the hydration-dehydration method and subsequent calcination at 600 °C. Comprehensive characterization of the obtained catalyst was conducted using: X-ray powder diffractometry (XRD), X-ray fluorescence (XRF), Fourier-transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), N2 physisorption, and Hg-porosimetry. Structural, morphological, and textural results showed that the obtained catalyst exhibited high porosity and regular dispersity of plate-like CaO as an active species. The obtained optimal residence time, catalyst concentration, and methanol/oil volume ratio for the continuous reaction in microreactor were 10 min, 0.1 g g-1, and 3:1, respectively. The analysis of variance (ANOVA) showed that the obtained reduced quadratic model was adequate for experimental results fitting. The reaction in the microreactor was significantly intensified compared to a conventional batch reactor, as seen through the fatty acid methyl esters (FAMEs) content after 10 min, which was 51.2% and 18.6%, respectively.
RESUMO
BACKGROUND: Growing challenges of resource depletion, food security and environmental protection are putting stress on the development of biorefinery processes for bioprocessing of residues from food and agro-industry into value-added products. In this study, the simultaneous production of lactic acid (LA) and livestock feed on a combined substrate based on molasses and potato stillage by Lactobacillus paracasei NRRL B-4564 immobilized onto sunflower seed hull (SSH), brewer's spent grain (BSG) and sugar beet pulp (SBP) was studied. RESULTS: The highest total LA concentration of 399 g L-1 with overall productivity of 1.27 g L-1 h-1 was achieved in repeated batch fermentation by SBP-immobilized biocatalyst, followed by BSG- and SSH-immobilized cells. Fermentation improved the content of proteins and ash, and decreased the content of fibers in all three support materials. In addition, the fermentation had favorable effect on in vitro dry matter digestibility and energy values of SSH and BSG. According to assessment of probiotic potential, L. paracasei demonstrated a favorable probiotic profile, exhibiting high resistance to simulated ruminant digestive tract and significant antioxidant and antimicrobial activity. CONCLUSIONS: The proposed strategy enables valorization of agro-industrial residues as value-added ruminant feed and simultaneous LA production. Following principles of circular economy, the developed process combines different raw materials and integrates them into a biorefinery process, improving the overall profitability and productivity. © 2019 Society of Chemical Industry.
