•Improved carbohydrase production by Aspergillus niger for cheap soy-meal processing.•Arrhenius-law activation energy for growth determined as 28.7 kcal/mol.•Fastest doubling time (2.1 h) at 30 °C ...but higher enzyme yield at 25 °C.•pH <2.6 limited pectinase synthesis; rapid pectinase degradation at pH > 5.5 & C limitation.•α-Galactosidase production relied on inducers from hydrolysis by pectinase.
Soybean is a most promising sustainable protein source for feed and food to help meet the protein demand of the rapidly rising global population. To enrich soy protein, the environment-friendly enzymatic processing requires multiple carbohydrases including cellulase, xylanase, pectinase, α-galactosidase and sucrase. Besides enriched protein, the processing adds value by generating monosaccharides that are ready feedstock for biofuel/bioproducts. Aspergillus could produce the required carbohydrases, but with deficient pectinase and α-galactosidase. Here we address this critical technological gap by focused evaluation of the suboptimal productivity of pectinase and α-galactosidase. A carbohydrases-productive strain A. niger (NRRL 322) was used with soybean hull as inducing substrate. Temperatures at 20 °C, 25 °C and 30 °C were found to affect cell growth on sucrose with an Arrhenius-law activation energy of 28.7 kcal/mol. The 30 °C promoted the fastest cell growth (doubling time = 2.1 h) and earliest enzyme production, but it gave lower final enzyme yield due to earlier carbon-source exhaustion. The 25 °C gave the highest enzyme yield. pH conditions also strongly affected enzyme production. Fermentations made with initial pH of 6 or 7 were most productive, e.g., giving 1.9- to 2.3-fold higher pectinase and 2.2- to 2.3-fold higher α-galactosidase after 72 h, compared to the fermentation with a constant pH 4. Further, pH must be kept above 2.6 to avoid limitation in pectinase production and, in the later substrate-limiting stage, kept below 5.5 to avoid pectinase degradation. α-Galactosidase production always followed the pectinase production with a 16-24 h lag; presumably, the former relied on pectin hydrolysis for inducers generation. Optimal enzyme production requires controlling the transient availability of inducers.
Display omitted
•Single enzymatic process to separate oil, protein and carbohydrate from soybean.•Recovered oil bodies and protein bodies without disrupting their structure.•Carbohydrates are ...recovered in hydrolyzed form.•Simplified processing and unified the product properties for more effective subsequent uses.
To maximize value and minimize waste in soy processing, all major soybean components, i.e., oil, protein and carbohydrate, should be collected and utilized. Existing processing was originally designed to maximize oil extraction. It tends to make protein and carbohydrate separation from remaining meal more difficult and reduce their value. In this study, a single-step sonication-assisted enzyme processing was developed to separate and collect intact oil bodies, protein bodies and hydrolyzed carbohydrates from soybeans. Confocal laser scanning microscopic observations confirmed enzymatic destruction of cell wall and separation of oil bodies and protein bodies by centrifugation. Distributions of oil, protein and carbohydrate were quantitated in the top oil/cream layer, bottom protein-enriched precipitates, and the middle aqueous solution. Effects of the soybean particle size and the concentration of an Aspergillus niger enzyme were investigated. A pulsed ultrasonic treatment at 1.5 W/ml, for 5 min every 3 h during the enzyme processing, was found to significantly improve the performance and separation of oil bodies from protein. 87% of oil bodies were collected from cracked particles of 0.42–1.19 mm in size using, per g particles, 2 ml enzyme that contained 0.62 FPU/ml cellulase, 93 U/ml xylanase, 5.8 U/ml pectinase and 6.4 U/ml α-galactosidase.
•Framework to direct enzyme production leveraging pH profile.•Production of a mixture of multiple carbohydrases from one fungal strain.•Developed a pH control strategy to direct high pectinase and ...α-galactosidase production.
Aspergillus foetidus was found to have different optimal pH conditions for producing different carbohydrases including cellulase, xylanase, pectinase, α-galactosidase, polygalacturonase, and invertase. Designs to trigger these conditions sequentially using controlled pH gradients were evaluated for directing the culture through multiple production stages optimal for different enzymes. For production of enzyme mixtures with particularly high pectinase and α-galactosidase activities, for more effective hydrolysis of the complex carbohydrate in soybean meal, the best method tested was a pH gradient started at pH 7.0, decreased to pH 6.0 over 72 h, held constant for 24 h, and then decreased to pH 5 over 24 h.
The International Pseudomonas aeruginosa Consortium is sequencing over 1000 genomes and building an analysis pipeline for the study of Pseudomonas genome evolution, antibiotic resistance and ...virulence genes. Metadata, including genomic and phenotypic data for each isolate of the collection, are available through the International Pseudomonas Consortium Database (http://ipcd.ibis.ulaval.ca/). Here, we present our strategy and the results that emerged from the analysis of the first 389 genomes. With as yet unmatched resolution, our results confirm that P. aeruginosa strains can be divided into three major groups that are further divided into subgroups, some not previously reported in the literature. We also provide the first snapshot of P. aeruginosa strain diversity with respect to antibiotic resistance. Our approach will allow us to draw potential links between environmental strains and those implicated in human and animal infections, understand how patients become infected and how the infection evolves over time as well as identify prognostic markers for better evidence-based decisions on patient care.
PDF
