No abstract

In microalgal cultivation, measuring cell numbers as a means to monitor growth rates is a long-standing problem. Many automated counting systems and schemes have been developed; among these are image analysis systems. However, such imaging systems have presented difficulties in dealing with the complexities of computer recognition of individual microscopic cells. It is known that the coloration of microalgae suspension is species specific and that color intensity increases are typically associated with increasing numbers. Using this qualitative insight, the present work describes the design, construction, and comparative performance of an inexpensive digital imaging system optimized for counting microalgal cells. The system circumvents the need to count individual cells and extracts cell numbers directly from the macroscopic color intensity of a microalgal suspension. The results suggest, using Isochrysis galbana (T-ISO) as an illustrative example, that this scheme is potentially useful for inexpensive and automated biomonitoring of microalgal cell numbers. Percentage difference comparisons with a standard Coulter Counter indicated that the three algorithms tested provided better than 10% accuracy over density thresholds of 1.52× 10 6 to 8.10×10 6 cells mL −1 with precision of 4% attainable at high density concentrations.

The utilization of several sugars in Escherichia coli is regulated by the Phosphotransferase System (PTS), in which diverse sugar utilization modules compete for phosphoryl flux from the general PTS proteins. Existing theoretical work predicts a winner-take-all outcome when this flux limits carbon uptake. To date, no experimental work has interrogated competing PTS uptake modules with single-cell resolution. Using time-lapse microscopy in perfused microchannels, we analyzed the competition between N-acetyl-glucosamine and sorbitol, as representative PTS sugars, by measuring both the expression of their utilization systems and the concomitant impact of sugar utilization on growth rates. We find two distinct regimes: hierarchical usage of the carbohydrates, and co-expression of the genes for both systems. Simulations of a mathematical model incorporating asymmetric sugar quality reproduce our metabolic phase diagram, indicating that under conditions of nonlimiting phosphate flux, co-expression is due to uncoupling of both sugar utilization systems. Our model reproduces hierarchical winner-take-all behaviour and stochastic co-expression, and predicts the switching between both strategies as a function of available phosphate flux. Hence, experiments and theory both suggest that PTS sugar utilization involves not only switching between the sugars utilized but also switching of utilization strategies to accommodate prevailing environmental conditions.

Purpose -The purpose of this paper is to develop a robotic system to feed aquatic organisms and measure water physicochemical parameters in experimental aquaculture ponds. Design/methodology/approach -A dispatcher unit dispenses a precise amount of food and control panel software schedules the tasks and operates the robot. In the control panel, the feeding and measuring schedule is defined and sent to the mobile robot and the amount of food is requested by the robot to the dispatcher for each pond. The robot travels automatically on a monorail to dispense the food and measure the water parameters. The data are transmitted to the control panel. The system can be remotely operated over the internet through a client-server software framework. Findings -The robotic system is a tool for delegating feeding and measuring tasks. This allows researchers and technicians time to focus on more substantive aquacultural research tasks. Research limitations/implications -Future improvement will include an automatic unit for cleaning sensors between ponds to minimize the risk of cross-contamination. Practical implications -The system systematized feeding and measuring tasks, minimized human error, and optimized the use of resources for aquacultural experimentation. The robotic system can be programmed for a variety of experimental conditions, such as the delivery of different diets at diverse schedules. Originality/value -The proposed robot was tested for feeding freshwater redclaw crayfish (Cherax quadricarinatus) and monitored the water parameters in real time. Based on the field results, the robotic system provided a reliable and robust device for aquacultural research applications.

An open-field cultivation combined-type aquaponic system (OCAS) was developed to effectively utilize saline groundwater and prevent soil salinization while ensuring food production in drylands. To achieve the sustainable food production of the OCAS in power-scarce areas, a stand-alone photovoltaic system (PVS) for the OCAS was designed through a feasibility study of utilizing solar energy to meet its power demand. As a case study, the OCAS was established in La Paz, Baja California Sur, Mexico, with power consumption 22.72 kWh/day and annual average daily global horizontal irradiation (GHI) 6.12 kWh/m2/day, considering the 2017 meteorological data. HOMER software was employed for performance analysis and techno-economic evaluation of an appropriate PVS. Thousands PVS configurations were evaluated in terms of total net present cost (NPC) and levelized cost of energy (COE). The PVS that fulfilled the power demand and had the smallest NPC was proposed, for which the NPC and COE were calculated as $46,993 and $0.438/kWh, respectively. The relationship between its annual power supply and power demand of the OCAS was also analyzed in detail. It was found that the operation hours and the amount of power generation by the proposed PVS were 4156 h and 19,106 kWh in one year. Additionally, it was predicted that the excess power would occur almost every afternoon and reach 43% of the generated power. Therefore, the COE can be further reduced by rationally utilizing the excess power during operation.