Engineering <i>Saccharomyces cerevisiae</i> for co-utilization of D-galacturonic acid and D-glucose from citrus peel waste

Pectin-rich agricultural byproducts are ideal feedstocks for biobased chemicals production. Here, the authors engineer the yeast, S. cerevisiae, in several steps to co-utilize d-galacturonic acid and d-glucose and demonstrate the potential of producing meso-galactaric acid from industrial orange peel

Engineering Saccharomyces cerevisiae for co-utilization of D-galacturonic acid and D-glucose from citrus peel waste.

Pectin-rich biomasses, such as citrus peel and sugar beet pulp, hold promise as inexpensive feedstocks for microbial fermentations as enzymatic hydrolysis of their component polysaccharides can be accomplished inexpensively to yield high concentrations of fermentable sugars and D-galacturonic acid (D-galUA). In this study, we tackle a number of challenges associated with engineering a microbial strain to convert pectin-rich hydrolysates into commodity and specialty chemicals. First, we engineer D-galUA utilization into yeast, Saccharomyces cerevisiae. Second, we identify that the mechanism of D-galUA uptake into yeast is mediated by hexose transporters and that consumption of D-galUA is inhibited by D-glucose. Third, we enable co-utilization of D-galUA and D-glucose by identifying and expressing a heterologous transporter, GatA, from Aspergillus niger. Last, we demonstrate the use of this transporter for production of the platform chemical, meso-galactaric acid, directly from industrial Navel orange peel waste

DANPY (dimethylaminonaphthylpyridinium): an economical and biocompatible fluorophore

Dyes with nonlinear optical (NLO) properties enable new imaging techniques and photonic systems. We have developed a dye (DANPY-1) for photonics applications in biological substrates such as nucleic acids; however, the design specification also enables it to be used for visualizing biomolecules. It is a prototype dye demonstrating a water-soluble, NLO-active fluorophore with high photostability, a large Stokes shift, and a favorable toxicity profile. A practical and scalable synthetic route to DANPY salts has been optimized featuring: (1) convergent Pd-catalyzed Suzuki coupling with pyridine 4-boronic acid, (2) site-selective pyridyl N-methylation, and (3) direct recovery of crystalline intermediates without chromatography. We characterize the optical properties, biocompatibility, and biological staining behavior of DANPY-1. In addition to stability and solubility across a range of polar media, the DANPY-1 chromophore shows a first hyperpolarizability similar to common NLO dyes such as Disperse Red 1 and DAST, a large two-photon absorption cross section for its size, substantial affinity to nucleic acids in vitro, an ability to stain a variety of cellular components, and strong sensitivity of its fluorescence properties to its dielectric environment.status: publishe

Alcohol, drug, and sexual risk behavior correlates of recent transactional sex among female black South African drug users

INTRODUCTION: Transactional sex among black South African women has become a mode of economic survival putting them at higher risk for HIV and other infectious disease. METHODS: In order to inform HIV interventions, drug and sexual risk behavior correlates of recent transactional sex among a descriptive epidemiological, cross-sectional sample of 189, black, South African women in Pretoria were examined using log binomial regression. RESULTS: Prevalence of HIV seropositivity was extremely high among non-transactional sex workers (47.1%) and transactional sex workers (54.6%), albeit not significantly different. Adjusted regression results indicated that the probability of transactional sex was greater for drug using women who tested positive for cocaine use (Adjusted Prevalence Ratio (APR)=1.3, 95% CI=1.1, 1.5) and knew of anyone who died of AIDS (APR =1.5, 95% CI 1.1, 2.1). The probability of transactional sex was lower for female drug users who reported greater education (APR =0.6, 95% CI= 0.4, 0.8), condom use in their first sexual encounter (APR =0.7, 95% CI=0.6, 1.0) or reported a recent steady sexual partnership (APR =0.8, 95% CI=0.7, 0.9). CONCLUSIONS: Drug use-related interventions for female transactional sex workers may need to focus on methods for the reduction of not only drug use, especially cocaine use, but also the reduction of sexual risk behaviors.Funding for this study was provided by NIDA’s Southern Africa Initiative as a supplement to a parent study conducted in the US (R01DA014498) and from the Drug Dependence Epidemiology Training Grant (T32DA007292). The authors wish to thank Dr. Leah Floyd for her work on this study