Enhanced bioremediation of acid mine-influenced groundwater with micro-sized emulsified corn oil droplets (MOD) and sulfate-reducing bacteria (Desulfovibrio vulgaris) in a microcosm assay.

High concentrations of metals and sulfates in acid mine drainage (AMD) are the cause of the severe environmental hazard that mining operations pose to the surrounding ecosystem. Little study has been conducted on the cost-effective biological process for treating high AMD. The current research investigated the potential of the proposed carbon source and sulfate reduction bacteria (SRB) culture in achieving the bioremediation of sulfate and heavy metals. This work uses individual and combinatorial bioaugmentation and bio-stimulation methods to bioremediate acid-mine-influenced groundwater in batch microcosm experiments. Bioaugmentation and bio-stimulation methods included pure culture SRB (Desulfovibrio vulgaris) and microsized oil droplet (MOD) by emulsifying corn oil. The research tested natural attenuation (T 1), bioaugmentation (T2), biostimulation (T3), and bioaugmentation plus biostimulation (T4) for AM-contaminated groundwater remediation. Bioaugmentation and bio-stimulation showed the greatest sulfate reduction (75.3%) and metal removal (95-99%). Due to carbon supply scarcity, T1 and T2 demonstrated 15.7% and 27.8% sulfate reduction activities. Acetate concentrations in T3 and T4 increased bacterial activity by providing carbon sources. Metal bio-precipitation was substantially linked with sulfate reduction and cell growth. SEM-EDS study of precipitates in T3 and T4 microcosm spectra indicated peaks for S, Cd, Mn, Cu, Zn, and Fe, indicating metal-sulfide association for metal removal precipitates. The MOD provided a constant carbon source for indigenous bacteria, while Desulfovibrio vulgaris increased biogenic sulfide synthesis for heavy metal removal.

Effect of hydrothermal treatment on physicochemical properties of amorphous granular potato starch (AGPS).

Using restructuring technology, A- or B-type crystalline granular potato starch was produced from amorphous granular potato starch (AGPS). AGPS was prepared using ethanol-heat processing, and hydrothermal treatments were performed with different moisture contents (18, 29, 200% d.b.) and temperatures (4, 25, 40, 60, 80 °C) for 3 weeks. AGPS showed no endothermic peak in a DSC thermogram, while hydrothermally treated AGPS (HAGPS) revealed endothermic peaks. In X-ray diffraction, AGPS displayed an amorphous pattern, and HAGPS displayed A- or B-type crystalline patterns depending on treatment temperature and moisture content. Neither AGPS nor HAGPS had typical RVA pasting curves, and their viscosities gradually increased. Raman spectroscopy and FT-IR confirmed that ordered structure and crystalline regions increased in HAGPS. Resistant starch (RS) and slowly digestible starch (SDS) contents of HAGPS increased but rapidly digestible starch (RDS) content decreased compared to AGPS. These results elucidated that hydrothermal treatment could change the physicochemical properties of AGPS and produce an identical material, such as granular potato starch with A-type and B-type crystalline granular potato starch.

Preparation and characterization of amorphous granular potato starches (AGPS) and cross-linked amorphous granular potato starches (CLAGPS).

Amorphous granular potato starch (AGPS) was prepared through heat treatment of native potato starch (NPS) at 94°C with 53% EtOH, while cross-linked amorphous granular potato starch (CLAGPS) was prepared through cross-linking of NPS with sodium trimetaphosphate/sodium tripolyphosphate (STMP/STPP, 99:1) and heat treatment. Light and polarized microscopy showed that both AGPS and CLAGPS maintained their granule shapes but lost birefringence. DSC and XRD of both AGPS and CLAGPS also revealed complete gelatinization. On the other hand, CLAGPS exhibited no RVA pasting viscosity and AGPS had a higher final viscosity than NPS or CLAGPS. AGPS had a higher RS content than gelatinized potato starch, while that of CLAGPS did not increase, despite the cross-linking modification. Thus, AGPS and CLAGPS had distinct physicochemical properties from each other and from NPS, suggesting their potential applicability to the food, textile, and paper industries.

Effect of high hydrostatic pressure treatment on conventional hydroxypropylation of maize starch.

Effect of high hydrostatic pressure (HHP) treatment on conventional hydroxypropylation of maize starch was investigated. Three groups, 'Con' group (conventional hydroxypropylation), 'HHP-Con' group (HHP treatment before conventional hydroxypropylation), and 'Con-HHP' group (HHP treatment after conventional hydroxypropylation), were used in this work. The degree of substitution (DS) increased over the reaction time in all groups. Swelling power and solubility were high in HHP treated groups compared to Con group because HHP treatment weakens the binding forces inside starch granule. In the results of RVA, the Con-HHP group showed a lower pasting temperature and a higher breakdown and viscosity than the other groups. Pre- and post HHP-treatments altered the physicochemical properties of hydroxypropylated maize starch. Hydrophilic and bulky hydroxypropyl groups may weaken the bindings in the granule, while the HHP treatment promoted the collapse of granules and accelerated the leaching of intra-soluble materials.