Browsing by Author "Lalov I."
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Item DEVELOPMENT OF SIMPLIFIED MODELS FOR OPTIMIZATION OF BIOCHEMICAL METHANE POTENTIAL PROCEDURE(2022-01-01) Velichkova P.; Ivanov T.; Lalov I.Anaerobic digestion (AD) can be used to convert biomass materials into methane for energy recovery and achieve waste stabilization and environment stress reduction. The effect of substrate/inoculum ratio, temperature and trace elements on the biochemical methane potential (BMP) was evaluated through the calculation of performance parameters by using three simplified mathematical models. The Modified Gompertz equation, the Logistic equation and Reaction curve (Transference) models were all used with experimental data from the BMP determination. The substrate was vinasse with COD 216 g O2 L-1, obtained as by-product in wine distillation process. The lag time phase, maximum rate of biogas production and maximal potential biogas production was estimated in each experiment by application of mathematical models. The obtained results indicate that the use of models allow accurate determination of parameters in BMP determination. In case with vinasse the modified Gompertz model fits better than others.Item ESTIMATION OF BIOCHEMICAL METHANE POTENTIAL OF HIGH PROTEIN SPIRULINA BIOMASS(2023-01-01) Ivanov T.; Lalov I.Biomass from microalgae is a promising feedstock for energy production through anaerobic digestion. The aim of this study was to determine the biochemical methane potential of Spirulina biomass. Тhe investigated biomass is characterized by a high protein content and a low carbon/nitrogen ratio. In order to improve the biodegradability of the biomass, the fresh biomass was pre-treated by thermolysis. Although a yield of 0.295 L CH4 g-1 VSS was obtained in the initial experiments, subsequent batch processes showed a drop in yield, slowing until the complete cessation of the methanation process. The main reason for the problems is the inhibition from high concentration of ammonium ions. After regeneration of the methanogenic consortium with vinasse substrate, an increase in yield to 0.445 L CH4 g-1 VSS was observed. The use of pretreated biomass resulted in an unexpected yield reduction effect. Application of vinasse as a co-substrate for methanation showed an increase in yield to 0.529 L CH4 g-1 VSS and stabilization of the processItem PORPHYRINE/SILVER NANOPARTICLES BASED PHOTOACTIVE ANTIBACTERIAL COATINGS(2023-01-01) Philipova N.; Georgiev N.; Ganchev D.; Lalov I.; Bryaskova R.A novel amino-modified protoporphyrin IX with included silver nanoparticles (PPIX-ED/AgNPs) complex was synthesized and used as a last layer for preparation of photoactive antibacterial coatings. The obtained PPIX-ED/ AgNPs complex was appropriately analyzed using various spectroscopic methods such as fluorescence analysis and infrared spectroscopy (ATR-FTIR). The size and morphology of the synthesized PPIX-ED/AgNPs complex were analyzed by Transmission electron microscopy (TEM) and dynamic light scattering (DLS). Then, the photoactive antibacterial coatings were obtained by deep coating procedure as the last layer consists of PPIX-ED/AgNPs complex, which is expected to possess strong antibacterial activity. The EDX-SEM analysis was employed to prove the deposition of the layers and nanoindentation analysis was used to determine their mechanical properties. The antibacterial properties of the photoactive coatings against G. negative E. coli and G. positive B. Subtilis were determined using disk diffusion method (DDM).Item Preparation of chitosan beads for trypsin immobilization(2014-04-16) Kamburov M.; Lalov I.The present study deals with the potential application of chitosan macrobeads for immobilization of trypsin. Macrobeads were prepared by precipitation and their mechanical properties were improved by covalent crosslinking using glutaraldehyde. Scanning electron microscopy studies showed that the beads size varied between 2.5 mm and 3.5 mm depending on the chitosan content and molar excess of glutaraldehyde. Trypsin (EC.3.4.21.4) was chosen as model enzyme for immobilization on the chitosan gel beads pre-activated with glutaraldehyde. Catalytic properties and kinetic parameters of free and immobilized trypsin were determined and the impact of various technological parameters on enzyme activity was investigated. The obtained results showed that the optimal pH and temperature for the hydrolytic reaction catalyzed by immobilized trypsin for low molecular weight substrates were pH 8.0 and 50oC, respectively. The effect of substrate concentration was also studied and the values of the constants thus determined were: Km=1,54 mM/L and Vmax – 3.3 μM/min.Item RYEGRASS AS A FEEDSTOCK FOR BIOETHANOL PRODUCTION(2023-01-01) Ivanov T.; Petrin S.; Lalov I.In current paper a comparative study of bioethanol yields from ryegrass biomass by different type of pretreatment and enzyme hydrolysis is done. Acidic and alkali hydrolysis was used as a pretreatment of this feedstock. Cellulase blend 10 FPU g-1 dry matter was used for enzyme hydrolysis. The pre-treatment was conducted by autoclaving for 20 minutes at 121°C. Best results were obtained by pretreatment with 1 % HCl and 1 % NaOH. Hydrolysate obtained by pretreatment with hydrochloric acid contained 33.6 mg mL-1 reducing sugars, and that obtained by pretreatment with base - 29.0 mg mL-1. Both hydrolysates were found to be suitable substrates for bioethanol generation, where 5.55 g ethanol/100 g dry matter was produced from grass hydrolysate obtained by acidic hydrolysis followed by enzyme hydrolysis and from alkali pretreated hydrolysate-4.73 g ethanol/100 g dry matter. The results demonstrated that ryegrass biomass is suitable feedstock for bioethanol production.