RESUMEN
Ongoing challenges with reproducible human norovirus cultivable assays necessitate the use of surrogates, such as feline calicivirus (FCV-F9) and Tulane virus (TV), during inactivation studies. Chlorine alternates used as control strategies include aqueous and gaseous ozone. This study aimed at determining the inactivation of FCV-F9 and TV by a portable ozone-generating device. FCV-F9 (â¼8 log PFU/mL) or TV (â¼6 log PFU/mL) in sterile-low-organic matter-containing-water was treated for 0-5 min, or in sterile-water containing newborn calf serum (high-organic matter/protein) for 0-38 min with â¼1 ppm ozone (pH 7-6). Infectivity was determined from triplicate treatments using plaque assays. FCV-F9 titers significantly decreased by 6.07 log PFU/mL after 5 min in ozonated low-organic-matter-containing-water and was non-detectable (≤2 log PFU/mL) after 36 min treatments in high-organic-matter-containing water (p < 0.05). TV titers decreased by 4.18 log PFU/mL after 4 min in ozonated low-organic-matter water (non-detectable after 4.5 min) and were non-detectable after 22.5 min treatments of high-organic-matter-containing water (p < 0.05). Overall, â¼1 ppm aqueous ozone significantly decreased FCV-F9 by >6 log PFU/mL after 5 min, TV to non-detectable levels (≤2 log PFU/mL) after 4.5 min and required longer treatments (>32 and >20 min, respectively) for ≥4 log reduction in high-organic-matter-containing water (p < 0.05). For ozone treatment of both viruses, the linear and Weibull models were similar for low-organic-load water, though the Weibull model was better for the high-organic load water. Prior filtration or organic load removal is recommended before ozonation for increased viral inactivation with decreased treatment-time.
RESUMEN
Hemicellulose, a structural polysaccharide and often underutilized co-product stream of biorefineries, could be used to produce prebiotic ingredients with novel functionalities. Since hot water pre-extraction is a cost-effective strategy for integrated biorefineries to partially fractionate hemicellulose and improve feedstock quality and performance for downstream operations, the approach was applied to process switchgrass (SG), hybrid poplar (HP), and southern pine (SP) biomass at 160°C for 60 min. As a result, different hemicellulose-rich fractions were generated and the chemical characterization studies showed that they were composed of 76-91% of glucan, xylan, galactan, arabinan, and mannan oligosaccharides. The hot water extracts also contained minor concentrations of monomeric sugars (≤18%), phenolic components (≤1%), and other degradation products (≤3%), but were tested for probiotic activity without any purification. When subjected to batch fermentations by individual cultures of Lactobacillus casei, Bifidobacterium bifidum, and Bacteroides fragilis, the hemicellulosic hydrolysates elicited varied responses. SG hydrolysates induced the highest cell count in L. casei at 8.6 log10 cells/ml, whereas the highest cell counts for B. fragilis and B. bifidum were obtained with southern pine (5.8 log10 cells/ml) and HP hydrolysates (6.4 log10 cells/ml), respectively. The observed differences were attributed to the preferential consumption of mannooligosaccharides in SP hydrolysates by B. fragilis. Lactobacillus casei preferentially consumed xylooligosaccharides in the switchgrass and southern pine hydrolysates, whereas B. bifidum consumed galactose in the hybrid poplar hydrolysates. Thus, this study (1) reveals the potential to produce prebiotic ingredients from biorefinery-relevant lignocellulosic biomass, and (2) demonstrates how the chemical composition of hemicellulose-derived sources could regulate the viability and selective proliferation of probiotic microorganisms.