Bioprocessing of Marine Chitinous Wastes for the Production of Bioactive Prodigiosin.

Recently, microbial prodigiosin (PG) has received much attention due to its numerous beneficial applications. The aim of this study was to establish the bioprocessing of marine chitinous wastes (MCWs) for the cost-effective preparation of PG. Of the MCWs, demineralized shrimp shell powders (de-SSP) were found to be a potential source of carbon/nitrogen (C/N) for PG production by bacterial fermentation using Serratia marcescens strains. Further, PG scale-up production was investigated in a 15 L bioreactor system, and the highest yield (6200 mg/L) was achieved during fermentation using 5 L of a novel-designed culture broth that included 1.60% C/N sources (a de-SSP/casein ratio of 7/3), 0.02% K2SO4, and 0.05% K2HPO4, with an initial pH of 6-7. Fermentation was conducted in the dark at 27.5 °C for 8.0 h. This study was the first to report on the utilization of shrimp wastes for cost-effective, large-scale (5 L/pilot) PG production with high productivity (6200 mg/L) in a short cultivation time. The combination of 0.02% K2SO4 and 0.05% K2HPO4 was also found to be a novel salt composition that significantly enhanced PG yield. The red compound was purified and confirmed as PG after analyzing its HPLC profile, mass, and UV/vis spectra. The purified PG was then tested for its bioactivities and showed effective anticancer activities, moderated antioxidant activities, and novel anti-NO effects.

Utilization of Crab Waste for Cost-Effective Bioproduction of Prodigiosin.

This study aimed to establish the culture process for the cost-effective production of prodigiosin (PG) from demineralized crab shell powder (de-CSP), a fishery processing byproduct created via fermentation. Among the tested PG-producing strains, Serratia marcescens TNU02 was demonstrated to be the most active strain. Various ratios of protein/de-CSP were used as the sources of C/N for PG biosynthesis. The PG yield was significantly enhanced when the casein/de-CSP ratio was controlled in the range of 3/7 to 4/6. TNU02 produced PG with a high yield (5100 mg/L) in a 15 L bioreactor system containing 4.5 L of a newly-designed liquid medium containing 1.6% C/N source (protein/de-CSP ratio of 3/7), 0.02% (NH4)2SO4, 0.1% K2HPO4, and an initial pH of 6.15, at 27 °C for 8 h in dark conditions. The red pigment was purified from the culture broth and then quantified as being PG by specific Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) and UV spectra analysis. The purified PG demonstrated moderate antioxidant and effective inhibition against four cancerous cell lines. Notably, this study was the first to report on using crab wastes for PG bioproduction with high-level productivity (5100 mg/L) in a large scale (4.5 L per pilot) in a short period of fermentation time (8 h). The salt compositions, including (NH4)2SO4 and K2HPO4, were also a novel finding for the enhancement of PG yield by S. marcescens in this report.

Author Correction: Bases of Bacterial Sodium Channel Selectivity Among Organic Cations.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Bases of Bacterial Sodium Channel Selectivity Among Organic Cations.

Hille's (1971) seminal study of organic cation selectivity of eukaryotic voltage-gated sodium channels showed a sharp size cut-off for ion permeation, such that no ion possessing a methyl group was permeant. Using the prokaryotic channel, NaChBac, we found some similarity and two peculiar differences in the selectivity profiles for small polyatomic cations. First, we identified a diverse group of minimally permeant cations for wildtype NaChBac, ranging in sizes from ammonium to guanidinium and tetramethylammonium; and second, for both ammonium and hydrazinium, the charge-conserving selectivity filter mutation (E191D) yielded substantial increases in relative permeability (PX/PNa). The relative permeabilities varied inversely with relative Kd calculated from 1D Potential of Mean Force profiles (PMFs) for the single cations traversing the channel. Several of the cations bound more strongly than Na+, and hence appear to act as blockers, as well as charge carriers. Consistent with experimental observations, the E191D mutation had little impact on Na+ binding to the selectivity filter, but disrupted the binding of ammonium and hydrazinium, consequently facilitating ion permeation across the NaChBac-like filter. We concluded that for prokaryotic sodium channels, a fine balance among filter size, binding affinity, occupancy, and flexibility seems to contribute to observed functional differences.

Anaerobic treatment of hydrothermally solubilised sugarcane bagasse and its kinetic modelling.

The aim of this study was the evaluation of anaerobic treatment for the soluble organics generated from a steam-explosion pre-treatment of sugarcane bagasse. The batch analysis revealed that about 50% of the organics was possible to be degraded into methane whilst the rest was biologically inert and composed of mostly lignin. Based on the experiment a kinetic model composed of 14 kinds of soluble substances and 5 kinds of anaerobic microorganisms was developed. The model was used to simulate the process performance of a continuous anaerobic bioreactor with MLSS concentration at 2500-15,000mg/L. The simulation indicated that the bioreactor could receive the influent until 0.4kg-COD/kg-MLSS/d of loading without significant deterioration of methane conversion. By addition of powdered activated carbon, the rest of unbiodegradable soluble organics and dark brown colour in the effluent were removed to 840mg-C/L and 760 unit respectively at adsorption of 190mg-C/g-PAC and 1200unit/g-PAC.