Addition of Fillers to Sodium Alginate Solution Improves Stability and Immobilization Capacity of the Resulting Calcium Alginate Beads.

BACKGROUND: Although advantages of immobilization of cells through entrapment in calcium alginate gel beads have already been demonstrated, nevertheless, instability of the beads and the mass transfer limitations remain as the major challenges. OBJECTIVE: The objective of the present study was to increase the stability, porosity (reduce mass transfer limitation), and cell immobilization capacity of calcium alginate gel beads. MATERIALS AND METHODS: Sodium alginate was mixed with various concentrations of the starch or sugar and gelled in 2% calcium chloride solution. During the gelling and curing, the starch or sugar leached out of the beads and created micro-pores. RESULTS: Micro-porous beads prepared with starch were more stable and had higher immobilization capacity than those prepared with sugar. After 24 hours of incubation (curing) of the micro-porous beads prepared with starch in calcium alginate, the solubilization time in citrate buffer was 93 minutes compared to 41 minutes for the control beads (without starch). The compressive strength of the micro-porous beads was also higher (5.62 Mpa) than that of the control beads (5.54 Mpa). The optimal starch concentration for cell immobilization was 0.4%. With this starch concentration, the immobilized Bacillus subtilis and Saccharomyces cerevisiae cell densities were 5.6 × 109 and 1.2 × 108 cells/beads, respectively. These values were 36.5% and 74% higher than the value obtained for the control beads. This method of immobilization resulted in more uniform cell distribution. CONCLUSION: Addition of starch to the sodium alginate solution before gelation in calcium chloride solution increased the stability of the beads, increased the immobilized cell density, and resulted in a more uniform cell distribution in the beads.

Experimental and In-Silico Investigation of Anti-Microbial Activity of 1-Chloro-2-Isocyanatoethane Derivatives of Thiomorpholine, Piperazine and Morpholine.

The Antibiogram properties of 1-chloro-2-isocyanatoethane derivatives of thiomorpholine (CTC), piperazine (CPC) and morpholine (CMC) were evaluated by the approved agar well diffusion, the minimum inhibitory concentration (MIC) and in silico techniques. A total of fourteen microbial cultures consisting of ten bacteria and four yeast strains were used in the biological study while affinity of the compounds for DNA gyrase, a validated antibacterial drug target, was investigated by docking method. Results indicate that both thiomorpholine and piperazine had zero activity against the Gram negative organisms tested. With morpholine, similar result was obtained except that cultures of Escherichia coli (ATCC 15442) and Salmonella typhi (ATCC 6539) presented with weak sensitivity (7-8 mm) as shown by the inhibition zone diameter (IZD) measurement. The Gram positive organisms were more sensitive to morpholine than the other compounds. The highest IZD values of 15-18 mm were achieved except for Streptococcus pneumoniae (ATCC 49619) in which mobility of the compound stopped after 12 mm. S. pneumoniae was resistant to both thiomorpholine and piperazine. The yeast strains were not sensitive to any of the studied compounds investigated. The MIC tests evaluated against a reference antibiotic show that while morpholine was most active at 4 µg.ml-1 against both B. cereus ATCC (14579) and B. subtilis, the least active compound was thiomorpholine which inhibited S. aureus (ATCC 25923) at 64 µg.ml-1. The three compounds demonstrated high affinity for the target protein (DNA gyrase) ranging from -4.63 to -5.64 Kcal/mol and even showed better ligand efficiencies than three known antibiotics; chlorobiocin, ciprofloxacin and tetracycline. This study identified the studied compounds as potential antibiotic leads with acceptable physicochemical properties and gave the molecular basis for the observed interactions between the compounds and the target protein which can be harnessed in structural optimization process.

Treatment of Palm Oil Mill Effluent by a Microbial Consortium Developed from Compost Soils.

A method for the aerobic treatment of palm oil mill effluent (POME) was investigated in shake-flask experiments using a consortium developed from POME compost. POME was initially centrifuged at 4,000 g for 15 min and the supernatant was enriched with (NH4)2SO4 (0.5%) and yeast extract (0.25%) to boost its nitrogen content. At optimum pH (pH 4) and temperature (40°C) conditions, the chemical oxygen demand (COD) of the effluent decreased from 10,350 to 1,000 mg/L (90.3%) after 7 days. The total bacterial population determined by plate count enumeration was 2.4 × 10(6) CFU/mL, while the fungal count was 1.8 × 10(3) colonies/mL. Bacteria of the genera Pseudomonas, Flavobacterium, Micrococcus, and Bacillus were isolated, while the fungal genera included Aspergillus, Penicillium, Trichoderma, and Mucor. When the isolated species were each inoculated into separate batches of the raw effluent, both pH and COD were unchanged. However, at 75 and 50% POME dilutions, the COD dropped by 52 and 44%, respectively, while the pH increased from 4 to 7.53. POME treatment by aerobic method is sustainable and holds promising prospects for cushioning the environment from the problems associated with the use of anaerobic systems.