Enzymatic Conversion of Sugar Beet Pulp: A Comparison of Simultaneous Saccharification and Fermentation and Separate Hydrolysis and Fermentation for Lactic Acid Production

U radu je ispitana učinkovitost proizvodnje mliječne kiseline tehnikama odvojene hidrolize i fermentacije, te istodobne saharifikacije i fermentacije pulpe šećerne trske, nusprodukta proizvodnje šećera. Pulpa šećerne trske hidrolizirana je s pomoću pet komercijalnih enzima, te je proveden niz pokusa na tresilici s pet odabranih sojeva bakterija mliječno-kiselog vrenja. Postignuti su različiti prinosi ukupnih reducirajućih šećera, ovisno o aktivnosti enzima prilikom razgradnje glavnih sastojaka pulpe. Najveći prinos nakon hidrolize i najmanji talog dobiveni su primjenom mješavine komercijalnih enzima Viscozyme® i Ultraflo® Max u omjeru 1:1. U postupku odvojene hidrolize i fermentacije bakterije mliječno-kiselog vrenja iskoristile su samo dio ugljikohidrata oslobođenih enzimskom hidrolizom za rast. U postupku se istodobne saharifikacije i fermentacije pri maloj dozi enzima smanjila akumulacija šećera. Smanjila se i opasnost od kataboličke represije ugljikom. Dobiveni rezultati pokazuju da je istodobna saharifikacija i fermentacija bolja od tehnike odvojene hidrolize i fermentacije, između ostalog i zbog manjih troškova i većeg prinosa. Prinos mliječne kiseline dobiven istodobnom saharifikacijom i fermentacijom (oko 30 g/L) bio je 80-90 % veći nego onaj dobiven odvojenom hidrolizom i fermentacijom.This study compares the efficiency of lactic acid production by separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF) of sugar beet pulp, a byproduct of industrial sugar production. In experiments, sugar beet pulp was hydrolyzed using five commercial enzymes. A series of shake flask fermentations were conducted using five selected strains of lactic acid bacteria (LAB). The differences in the activities of the enzymes for degrading the principal sugar beet pulp components were reflected in the different yields of total reducing sugars. The highest yields after hydrolysis and the lowest quantities of insoluble residues were obtained using a mixture (1:1) of Viscozyme® and Ultraflo® Max. In the SHF process, only a portion of the soluble sugars released by the enzymes from the sugar beet pulp was assimilated by the LAB strains. In SSF, low enzyme loads led to reduction in the efficiency of sugar accumulation. The risk of carbon catabolic repression was reduced. Our results suggest that SSF has advantages over SHF, including lower processing costs and higher productivity. Lactic acid yield in SSF mode (approx. 30 g/L) was 80–90 % higher than that in SHF

The Use of Acidic Hydrolysates after Furfural Production from Sugar Waste Biomass as a Fermentation Medium in the Biotechnological Production of Hydrogen

This study investigates a simultaneous processing of sugar beet pulp (SBP) for furfural, hydrogen and methane production using various pretreatment methods. In the experiments, sugar beet pulp was first subjected to thermal and thermochemical pretreatment at 140 °C. Then hydrolysates from these operations were investigated for their potential for methane and hydrogen production in batch tests. The experiments showed that thermal pretreatment of SBP resulted in the highest biogas and methane yields of 945 dm3/kg volatile solids (VS) and 374 dm3 CH4/kg VS, respectively, and a moderate hydrogen production of 113 dm3 H2/kg VS, which corresponded to a calculated energy production of 142 kWh/t; however, only low amount of furfural was obtained (1.63 g/L). Conversely, the highest furfural yield of 12 g/L was achieved via thermochemical pretreatment of SBP; however, biogas production from hydrolysate was much lower (215 dm3/kg VS) and contained only 67 dm3/kg VS of hydrogen. Meanwhile, in the experiment with lower amounts of sulfuric acid (2%) used for pretreatment, a moderate furfural production of 4 g/L was achieved with as high as 220 dm3/kg VS of hydrogen and the corresponding energy yield of 75 kWh/t

Structure and mechanical properties of nanofibrous ZrO2 derived from alternating field electrospun precursors

Nanofibrous zirconia (ZrO2) meshes were prepared from precursor fibers which were synthesized using the method of free-surface, high-yield alternating field electrospinning (AFES). The weight ratio of zirconyl chloride salt to polyvinylpyrrolidone (PVP) polymer in liquid precursors was investigated for its effect on the spinnability and formation of precursor fibers as well as on the resulting fibrous ZrO2. The precursor fiber generation measured at a rate up to 5.6 g/h was achieved with a single flat 25-mm diameter alternating current (AC) electrode, which corresponded to production of up to 1.5 g/h of fibrous ZrO2. The calcination process involved annealing the fibers at temperatures which ranged from 600 °C to 1000 °C and produced 0.1–0.2 mm thick fibrous ZrO2 meshes. Individual nanofibers were found to have diameters between 50 and 350 nm and either a tetragonal (t-ZrO2) or monoclinic (t-ZrO2) structure depending on the calcination temperature. The annealed meshes with total porosity between 98.0 ± 0.2% and 94.6 ± 0.2% showed little deformation or cracking. Tensile strength and modulus of fibrous t-ZrO2 meshes strongly depended on porosity and varied from 0.07 ± 0.03 MPa to 1.05 ± 0.3 MPa and from 90 ± 40 MPa to 388 ± 20 MPa, respectively. The m-ZrO2 meshes resulted similar moduli, but much lower strengths due to their brittleness. A power-law relationship between the elastic modulus and porosity of AFES-derived nanofibrous t-ZrO2 meshes, in comparison with other porous zirconia materials, was also investigated. The results of this study have demonstrated the feasibility of free-surface AFES in sizeable production of zirconia nanofibers and highly porous nanofibrous ceramic structures

Combined Yeast Cultivation and Pectin Hydrolysis as an Effective Method of Producing Prebiotic Animal Feed from Sugar Beet Pulp

An effective and ecological method for liberation of pectin-derived oligosaccharides (POS) from sugar beet pulp (SBP) was developed using enzymatic and microorganism-mediated biomass conversion. The POS may be applied in the production of prebiotic feed additives. Various yeast strains were screened for their capacity for protein synthesis and monosaccharide assimilation. Combined yeast cultivation and pectin hydrolysis were found to be an effective method of producing prebiotics. Separate enzymatic hydrolysis and fermentation of SBP resulted in the release of 3.6 g of POS per 100 g d.w., whereas the yield of POS acquired after the combined process was 17.9% higher, giving 4.2 g of POS per 100 g d.w. Introducing the yeast into the process improved hydrolysis performance due to lower enzyme inhibition by mono- and disaccharides. The prebiotic effect of the POS was assessed by in vitro fermentation using individual cultures of gastrointestinal bacteria. The POS in the SBP hydrolysate effectively promoted the growth of lactobacilli and bifidobacteria. A large increase in adherence to Caco-2 cells in the presence of POS was noted for beneficial Lactobacillus brevis strains, whereas pathogenic bacteria and yeast (C. albicans, C. lusitanie, C. pelliculosa), responsible for infections in breeding animals, showed much weaker adhesion

Concept for Recycling Waste Biomass from the Sugar Industry for Chemical and Biotechnological Purposes

The objective of this study was to develop a method for the thermally-assisted acidic hydrolysis of waste biomass from the sugar industry (sugar beet pulp and leaves) for chemical and biotechnological purposes. The distillates, containing furfural, can be catalytically reduced directly into furfurayl alcohol or tetrahydrofurfuryl alcohol. The sugars present in the hydrolysates can be converted by lactic bacteria into lactic acid, which, by catalytic reduction, leads to propylene glycol. The sugars may also be utilized by microorganisms in the process of cell proliferation, and the biomass obtained used as a protein supplement in animal feed. Our study also considered the effects of the mode and length of preservation (fresh, ensilage, and drying) on the yields of furfural and monosaccharides. The yield of furfural in the distillates was measured using gas chromatography with flame ionization detector (GC-FID). The content of monosaccharides in the hydrolysates was measured spectrophotometrically using enzymatic kits. Biomass preserved under all tested conditions produced high yields of furfural, comparable to those for fresh material. Long-term storage of ensiled waste biomass did not result in loss of furfural productivity. However, there were significant reductions in the amounts of monosaccharides in the hydrolysates

Improving Biorefinery Sustainability and Profitability by Cultivating Aquatic Plants on Ozonized Distillery Effluents

Industrial production of biogas offers a way to manage distillery leachate. The waste is usually subjected to anaerobic digestion for producing biogas. However, the effluent from anaerobic processes has high chemical oxygen demand (COD) and is harmful to the environment. An effective method of lowering COD is ozonation. Effluent from biogas plants after ozonation has the potential for use in breeding grounds for plants of the Lemnaceae family. Thus, they can provide a valuable additional source of biomass for the production of bioethanol. Lemna minor L. and Spirodela polyrhiza cultures were grown in media with the addition of 2.5% PFE, which had been treated by ozonation for between 6 and 50 min. Using ozonated effluent was an effective cultivation technique in all variants. The analyzed parameters were plant growth, chlorophyll index, fresh plant weight and photosynthetic traits (net photosynthesis, stomatal conductance, transpiration and concentration of intercellular CO2). The best growth of Lemna minor L. was observed in the media with PFE treated for 12 min. Similar effects were obtained for S. polyrhiza, with ozone treatment for 12 and 25 min. The results show the potential of using ozone-treated post-fermentation leachate as a supplement in culture media