Water concentration and rate of decrease in shiitake cultivation log during fruiting body development, as measured by MRI.

Large shiitake mushrooms (Lentinula edodes, pileus > 8 cm in diameter) are difficult to cultivate and account for only 3-5% of the total harvest. This study focused on the water absorption process within a log during the growth of fruiting bodies in order to increase the yield of large shiitake mushrooms. Konara oak logs (Quercus serrata, 85-95 mm in diameter, 290 mm in length) were inoculated with shiitake mycelium plugs and nine months later, young fruiting bodies developed, at which point the log was analyzed using magnetic resonance imaging (MRI) over a period of two weeks. The signal intensity and T1 and T2 relaxation time constants were determined from the acquired images, along with the distribution of water concentration within the entire log. The axial distributions of water concentrations in the log were higher in the 80 mm region around the fruiting body. The rate of decrease in water concentration indicated that water was supplied to the fruiting body from 80 mm axially in the upper half of the sapwood in the log. On the other hand, the water concentration in the heartwood did not decrease and the heartwood did not contribute to the water supply to the fruiting bodies.

A non-invasive method for measuring time-series of moisture concentrations in mycelial blocks during shiitake mushroom development using magnetic resonance imaging.

The moisture concentration in mycelial block is an important factor for increasing the yield of high-quality shiitake mushrooms (Lentinula edodes) with a pileus of 4-5cm or more in mycelial block cultivation. Here, we show a novel way to measure moisture concentration in mycelial blocks using magnetic resonance imaging (MRI). The culture medium was inoculated with Hokken No. 607 and mycelial blocks were incubated and their moisture concentration was measured using MRI. A method was developed to calculate the spatial distribution of moisture concentration inside the mycelial blocks by measuring the total water mass in the mycelial block using mass method and creating a calibration line. During the maturation phase of the mycelial block (46-98 days of incubation), the moisture concentration in the top region of the mycelial block decreased once at 66 days of incubation and then gradually increased. The increase in moisture concentration was due to mycelia decomposing the culture medium and producing water. During the growth period of the fruiting body, the moisture concentration in the periphery of the fruiting body increased and, conversely, the moisture concentration in the whole mycelial block decreased because water in the mycelial block moved into the fruiting body.

Enhanced water uptake in the longitudinal direction by shiitake mycelium in shiitake cultivation logs: water content distribution in logs measured by magnetic resonance imaging.

In the cultivation of shiitake mushrooms (Lentinula edodes), the farmer needs to know the time needed to water in order to adjust the water content of the logs. To study the enhanced water uptake in the longitudinal direction by shiitake mycelium in shiitake cultivation logs, six dried test logs (Quercus serrata, diameter of 38 to 48 mm, length of 110 to 118 mm) were used. Three test logs had shiitake mycelium grown on them, and the remaining three test logs had mold generated on them. Liquid water was supplied to the bottom surface of the test log which had its longitudinal direction along the line of gravity. Water content distribution in the logs was measured in chronological order using magnetic resonance imaging (MRI) with 1 Tesla. The calibration curve for converting the signal intensity of the MR image into the water content in the test log was determined by cutting the test log at 5-mm intervals and measuring the water content distribution using the mass method. Spatial distribution of the water content of the test log without shiitake mycelium depending on the cumulative water supply time was obtained, and the distribution shape was always concave corresponding to the exact solution of an unsteady one-dimensional diffusion equation with one diffusion coefficient. In the case of the test log in which shiitake mycelium grew, within a few hours after liquid water supply the water content increased in the whole region where shiitake mycelium grew, and the shape of the water content distribution in the longitudinal direction became convex. Based on observation of water penetration into logs by MRI and an optical microscope, it is believed that the driving force behind increased rise in liquid water in the longitudinal direction in the test log is the capillary force acting in vessels.

Enhanced water uptake in the longitudinal direction by shiitake mycelium in shiitake cultivation logs: increase in effective diffusion coefficient based on mass of liquid water uptake.

In the cultivation of shiitake mushrooms (Lentinula edodes), the farmer needs to know the time needed to water in order to adjust the water content of the logs. In this study, six test logs (Quercus serrata, diameter of 38-48 mm, length of 110-118 mm) were used, of which some were dried, some had shiitake mycelia grown on them, and some had mold generated on them. Liquid water was supplied to the test logs by placing the longitudinal direction of the test logs along the line of gravity and immersing the bottom of the test logs in water. Water uptake mass of the test logs was measured for 20 h. The effective diffusion coefficient, D eff, was calculated from the change in time of the water uptake mass using Fick's diffusion law. The D eff of test logs in which shiitake mycelium grew were 1.5-3.4 × 10-8 m2/s, and the values were 2.4-4.7 times higher than that for the dried log. On the other hand, the D eff of the moldy logs were 6.7-9.7 × 10-10 m2/s, which was 0.058-0.081 times that of dry test logs. Based on observation of water penetration into logs by magnetic resonance imaging (MRI) and an optical microscope, it is believed that the driving force behind liquid water rising in the longitudinal direction in the test log is the capillary force acting on a three-phase interface consisting of the inner wall surface of the vessel, liquid water and air. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00226-021-01313-6.

MRI visualization of shiitake mycelium growing in woodchip blocks used for shiitake mushroom cultivation.

In order to eliminate woodchip blocks where unwanted fungi have grown and select only blocks where shiitake mycelium are growing well, there is a need to develop a visualization technique for shiitake mycelium growing in woodchip blocks, and MRI is an obvious candidate technique. From the results of measurements of the woodchip bed in a small bottle (26 mm inside diameter) where shiitake mycelium was growing, the T1 relaxation time constant immediately after inoculation was 77.9 ±â€¯5.5 ms, and the value after about 10 to 20 days increased to 135.0 ±â€¯9.8 ms (the increase rate was 73%). The T1 maps of the wood-chip block (130 mm length, 75 mm height and 55 mm thickness) in which shiitake mycelium grew were calculated from T1 weighted images measured by changing TR from 28 to 400 ms. From the T1 maps of time series, it was found that the shiitake mycelium extended from the right-hand side to the left-hand side of the woodchip block in a planar manner. Furthermore, in a woodchip block in which penicillium was generated, since the T1 relaxation time constant of only the shiitake mycelium became longer, it was possible to visualize the shiitake mycelium distinctly from penicillium.

Two dimensional distribution measurement of electric current generated in a polymer electrolyte fuel cell using 49 NMR surface coils.

In order to increase the current density generated in a PEFC (polymer electrolyte fuel cell), a method for measuring the spatial distribution of both the current and the water content of the MEA (membrane electrode assembly) is necessary. Based on the frequency shifts of NMR (nuclear magnetic resonance) signals acquired from the water contained in the MEA using 49 NMR coils in a 7 × 7 arrangement inserted in the PEFC, a method for measuring the two-dimensional spatial distribution of electric current generated in a unit cell with a power generation area of 140 mm × 160 mm was devised. We also developed an inverse analysis method to determine the two-dimensional electric current distribution that can be applied to actual PEFC connections. Two analytical techniques, namely coarse graining of segments and stepwise search, were used to shorten the calculation time required for inverse analysis of the electric current map. Using this method and techniques, spatial distributions of electric current and water content in the MEA were obtained when the PEFC generated electric power at 100 A.

NMR measurement system including two synchronized ring buffers, with 128 rf coils for in situ water monitoring in a polymer electrolyte fuel cell.

A small radio-frequency (rf) coil inserted into a polymer electrolyte fuel cell (PEFC) can be used to acquire nuclear magnetic resonance (NMR) signals from the water in a membrane electrode assembly (MEA) or in oxygen gas channels in the PEFC. Measuring the spatial distribution of the water in a large PEFC requires using many rf probes, so an NMR measurement system which acquires NMR signals from 128 rf probes at intervals of 0.5 s was manufactured. The system has eight rf transceiver units with a field-programmable gate array (FPGA) for modulation of the excitation pulse and quadrature phase detection of the NMR signal, and one control unit with two ring buffers for data control. The sequence data required for the NMR measurement were written into one ring buffer. The acquired NMR signal data were then written temporarily into the other ring buffer and then were transmitted to a personal computer (PC). A total of 98 rf probes were inserted into the PEFC that had an electrical generation area of 16 cm × 14 cm, and the water generated in the PEFC was measured when the PEFC operated at 100 A. As a result, time-dependent changes in the spatial distribution of the water content in the MEA and the water in the oxygen gas channels were obtained.

Development of an eight-channel NMR system using RF detection coils for measuring spatial distributions of current density and water content in the PEM of a PEFC.

The water generation and water transport occurring in a polymer electrolyte fuel cell (PEFC) can be estimated from the current density generated in the PEFC, and the water content in the polymer electrolyte membrane (PEM). In order to measure the spatial distributions and time-dependent changes of current density generated in a PEFC and the water content in a PEM, we have developed an eight-channel nuclear magnetic resonance (NMR) system. To detect a NMR signal from water in a PEM at eight positions, eight small planar RF detection coils of 0.6 mm inside diameter were inserted between the PEM and the gas diffusion layer (GDL) in a PEFC. The local current density generated at the position of the RF detection coil in a PEFC can be calculated from the frequency shift of the obtained NMR signal due to an additional magnetic field induced by the local current density. In addition, the water content in a PEM at the position of the RF detection coil can be calculated by the amplitude of the obtained NMR signal. The time-dependent changes in the spatial distributions were measured at 4 s intervals when the PEFC was operated with supply gas under conditions of fuel gas utilization of 0.67 and relative humidity of the fuel gas of 70%RH. The experimental result showed that the spatial distributions of the local current density and the water content in the PEM within the PEFC both fluctuated with time.