Tien-Chieh Hung

Hydrolysis of microalgae cell walls for production of reducing sugar and lipid extraction.

In this study, cell walls of microalgae were hydrolyzed for the production of reducing sugar by cellulase, which was immobilized onto an electrospun polyacrylonitrile (PAN) nanofibrous membrane. Since the nitrile groups of the PAN membrane were activated by the amidination reaction and covalent binding to the amino groups of the cellulase, electrospun PAN nanofibrous membranes with a high specific surface area were applied as supports for the immobilization. Under the optimal hydrolysis conditions, the immobilized cellulase performed its hydrolyzing conversion at 62%, and the hydrolysis yield remained at 40% after five times of reuse. Additionally, microalgal lipid extraction efficiency increased to around 56% from 32% dramatically after cell wall hydrolysis. These results demonstrate the efficacy and feasibility of the proposed applications in hydrolysis process followed with lipid extraction.

Effects of biomass weight and light intensity on the performance of photosynthetic microbial fuel cells with Spirulina platensis.

Microalgae Spirulina platensis were attached to the anode of a membrane-free and mediator-free microbial fuel cell (MFC) to produce electricity through the consumption of biochemical compounds inside the microalgae. An increase in open circuit voltage (OCV) was observed with decreasing light intensity and optimal biomass area density. The highest OCV observation for the MFC was 0.39 V in the dark with a biomass area density on the anode surface of 1.2 g cm(-2). Additionally, it was observed that the MFC with 0.75 g cm(-2) of biomass area density produced 1.64 mW m(-2) of electrical power in the dark, which is superior to the 0.132 mW m(-2) produced in the light. Which also means the MFC can be applied to generate electrical power under both day and night conditions.

Immobilization of cellulase onto electrospun polyacrylonitrile (PAN) nanofibrous membranes and its application to the reducing sugar production from microalgae

This study demonstrates a method to prepare an immobilized cellulase by using an electrospun polyacrylonitrile (PAN) nanofibrous membrane as the support. To obtain an immobilized cellulase with high hydrolytic activity, the immobilization conditions including activation time, enzyme concentration, immobilization time, and temperature were optimized. Under those conditions, the immobilized cellulase possessed a protein loading of 30 mg/g-support and a specific activity of 3.2U/mg-protein. After immobilization, the enzymatic stability of cellulase against pH and thermal stresses was improved. Fourier transform infrared spectroscopy (FTIR) measurements also revealed that the cellulase was covalently bonded to the supports. The immobilized cellulase was then used to hydrolyze cell wall of microalgae for the production of reducing sugars. Analyses using response surface methodology (RSM) show that the hydrolysis yield was affected by the reaction temperature, pH, and substrate/cellulase mass ratio, and a hydrolysis yield of 60.86% could be obtained at 47.85°C, pH 5.82, and a substrate/cellulase mass ratio of 40 g-substrate/g-cellulase. This result suggests that the proposed scheme for the cellulase immobilization has great potential for the application to the reducing sugar production.

Immobilization of lipase to chitosan beads using a natural cross-linker.

Abstract Genipin, a reagent of plant origin was used for the immobilization of lipase by cross‐linking to chitosan beads. The catalytic properties and operational and storage stabilities of the immobilized lipase were compared with the soluble lipase. Under optimum conditions, 198 µg protein was bound per g chitosan with a protein‐coupling yield of 35%. The hydrolytic activity was 10.8 U/g chitosan and the relative specific activity was 108%. The immobilized lipase showed better thermal and pH stabilities compared to the soluble form. The immobilized enzyme exhibited mass transfer limitations as reflected by a higher apparent Km value and a lower energy of activation. The immobilized enzyme retained about 74% of its initial activity after five hydrolytic cycles.

Bio-inspired particle separator design based on the food retention mechanism by suspension-feeding fish.

A new particle separator is designed using a crossflow filtration mechanism inspired by suspension-feeding fish in this study. To construct the model of the bio-inspired particle separator, computational fluid dynamics techniques are used, and parameters related to separator shape, fluid flow and particle properties that might affect the performance in removing particles from the flow, are varied and tested. The goal is to induce a flow rotation which enhances the separation of particles from the flow, reduce the particle-laden flow that exits via a collection zone at the lower/posterior end of the separator, while at the same time increase the concentration of particles in that flow. Based on preliminary particle removal efficiency tests, an exiting flow through the collection zone of about 8% of the influent flow rate is selected for all the performance tests of the separator including trials with particles carried by air flow instead of water. Under this condition, the simulation results yield similar particle removal efficiencies in water and air but with different particle properties. Particle removal efficiencies (percentage of influent particles that exit through the collection zone) were determined for particles ranging in size from 1 to 1500 µm with a density between 1000 and 1150 kg m(-3) in water and 2 and 19 mm and 68 and 2150 kg m(-3) in air. As an example, removal efficiencies are 66% and 64% for 707 µm diameter particles with a density of 1040 kg m(-3) in water and for 2 mm particles with a density of 68 kg m(-3) in air, respectively. No significant performance difference is found by geometrically scaling the inlet diameter of the separator up or down in the range from 2.5 to 10 cm.

Sub-lethal effects of herbicides penoxsulam, imazamox, fluridone and glyphosate on Delta Smelt ( Hypomesus transpacificus )

Concerns regarding non-target toxicity of new herbicides used to control invasive aquatic weeds in the San Francisco Estuary led us to compare sub-lethal toxicity of four herbicides (penoxsulam, imazamox, fluridone, and glyphosate) on an endangered fish species Delta Smelt (Hypomesus transpacificus). We measured 17β-estradiol (E2) and glutathione (GSH) concentrations in liver, and acetylcholinesterase (AChE) activity in brain of female and male fish after 6 h of exposure to each of the four herbicides. Our results indicate that fluridone and glyphosate disrupted the E2 concentration and decreased glutathione concentration in liver, whereas penoxsulam, imazamox, and fluridone inhibited brain AChE activity. E2 concentrations were significantly increased in female and male fish exposed to 0.21 μM of fluridone and in male fish exposed to 0.46, 4.2, and 5300 μM of glyphosate. GSH concentrations decreased in males exposed to fluridone at 2.8 μM and higher, and glyphosate at 4.2 μM. AChE activity was significantly inhibited in both sexes exposed to penoxsulam, imazamox, and fluridone, and more pronounced inhibition was observed in females. The present study demonstrates the potential detrimental effects of these commonly used herbicides on Delta Smelt.

Feasibility of Passive Integrated Transponder and Acoustic Tagging for Endangered Adult Delta Smelt

AbstractConservation and recovery of endangered species requires timely and defensible data to predict their responses to management actions. In the Sacramento–San Joaquin Delta, the population of Delta Smelt Hypomesus transpacificus, a species of management concern, has declined to a record low. Alternative research strategies are now sought to determine the efficacy of management actions. In this study, we assessed the feasibility of tagging cultured adult Delta Smelt as a potential surrogate for wild fish in field experiments. Preliminary experiments determined that anesthesia of Delta Smelt in 35 mg/L AQUI-S 20E for 4 min best facilitated tagging. The 28-d survival of Delta Smelt (n = 39) intracoelomically injected with passive integrated transponder (PIT) tags (8.4 mm, 0.03 g) was high (95%) and did not differ from untagged control fish; tag retention was 97%. Survival of Delta Smelt with injected (n = 40) and surgically inserted (n = 40) dummy acoustic transmitters (15.0 mm, 0.22 g) was significantl...

Adverse reproductive performance in zebrafish with increased bioconcentration of microcystin-LR in the presence of titanium dioxide nanoparticles

The aim of the present study was to investigate the reproductive effects of microcystin-LR (MCLR) in the presence of titanium dioxide nanoparticles (n-TiO2). Five-month-old zebrafish were exposed to MCLR (0, 0.5, 4 and 32 μg L−1) alone or combined with n-TiO2 (100 μg L−1) for 21 days. The accumulation of both n-TiO2 and MCLR was observed in the fish liver, brain and gonad. Enhanced bioconcentration of MCLR was measured in coexposure groups. Joint exposure to both n-TiO2 and MCLR significantly reduced the fecundity of adult fish compared to the MCLR-only treatment. Histopathological examination revealed no obvious change in the morphology of the ovary and testis, while a significant decline of estradiol (E2) and testosterone (T) levels as well as disordered transcription patterns of genes along the hypothalamus–pituitary–gonadal (HPG) axis was observed. N-TiO2 may act as a carrier of MCLR and increase its concentration upon coming in contact with zebrafish, which exacerbated the reproductive endocrine dysfunction as a consequence.

A Conservation Hatchery Population of Delta Smelt Shows Evidence of Genetic Adaptation to Captivity After 9 Generations

Genetic adaptation to captivity is a concern for threatened and endangered species held in conservation hatcheries. Here, we present evidence of genetic adaptation to captivity in a conservation hatchery for the endangered delta smelt (Fish Conservation and Culture Laboratory, University of California Davis; FCCL). The FCCL population is genetically managed with parentage analysis and the addition of wild fish each year. Molecular monitoring indicates little loss of genetic variation and low differentiation between the wild and conservation populations. Yet, we found an increase in offspring survival to reproductive maturity during the subsequent spawning season (recovery rate) in crosses that included one or both cultured parents. Crosses with higher levels of hatchery ancestry tend to produce a greater number of offspring that are recovered the following year. The recovery rate of a cross decreases when offspring are raised in a tank with fish of high levels of hatchery ancestry. We suggest changes in fish rearing practices at the FCCL to reduce genetic adaptation to captivity, as delta smelt numbers in the wild continue to decline and the use of FCCL fish for reintroduction becomes more likely.

Decline in Feeding Activity of Female Cultured Delta Smelt Prior to Spawning

AbstractAn observed decline in feeding behavior of Delta Smelt Hypomesus transpacificus due to spawning is presented here. At three different temperatures to which examined fish acclimated (10.2, 14.1, and 18.1°C), female Delta Smelt consistently showed significantly higher stomach content than male Delta Smelt when carrying early-stage eggs. However, a significant decline of feed intake was observed in female Delta Smelt when eggs ripened and were ready for spawning. These results indicate that female Delta Smelt tend to have high food consumption at the egg development stages but change behavior as eggs ripen. Possible causes for the change in feeding behavior are discussed.Received October 9, 2013; accepted January 11, 2014