Utilization of Corncob as an Immobilization Matrix for a Xylanolytic Yeast Strain.

Immobilization of microbial cells for the production of industrially important enzymes has been reported to offer the advantages of recyclability, higher yields and cost effectiveness. The search for an appropriate matrix that is affordable and easy to prepare is a significant topic in microbial biotechnology. Here, an abundant type of agro-industrial waste-corncob-was utilized as an immobilization matrix for the production of xylanase from an indigenous yeast strain, Saccharomyces cerevisiae MK-157. This is the first report describing xylanase production from immobilized S. cerevisiae. To render the corncob matrix more porous, alkaline pretreatment was undertaken and yeast cells were immobilized on the matrix by cultivating at 30 °C for 48 h in Sabouraud dextrose broth. After incubation, the immobilized matrix was transferred to mineral salt medium containing 1% xylan and incubated at 30 °C for 24 h. Xylanase production was determined in cell-free culture supernatant and the matrix was recycled for up to seven cycles. Moreover, xylanase-mediated saccharification was carried out using sugarcane bagasse as a substrate and the release of reducing sugars was monitored. The results showed that the immobilized yeast produced 4.97 IU mL-1 xylanase in the first production cycle, indicating a >tenfold increase compared to the free cells. Xylanase production further increased to its maximum levels (9.23 IU mL-1) in the fourth production cycle. Nonetheless, the cells retained 100% productivity for up to seven cycles. The volumetric and specific productivity of xylanase were also the highest in the fourth cycle. Scanning electron microscopy images revealed the rough surface of the untreated corncob, which became more porous after alkaline pretreatment. Immobilized yeast cells were also visible on the corncob pieces. The saccharification of a natural resource-sugarcane bagasse-using xylanase preparation yielded 26 mg L-1 of reducing sugars. Therefore, it can be concluded that yeast strains can yield sufficient quantities of xylanase, allowing possible biotechnological applications. Moreover, corncob can serve as a cost-effective matrix for industrially important yeast strains.

Computational vector fiducial for deflectometry system alignment.

One of deflectometry's cardinal strengths is its ability to measure highly dynamically sloped optics without needing physical null references. Accurate surface measurements using deflectometry, however, require precise calibration processes. In this Letter, we introduce an alignment technique using a computational fiducial to align a deflectometry system without additional hardware equipment (i.e., algorithmic innovation). Using the ray tracing program, we build relationships between the plane of the screen and detector and algorithmically generate a fiducial pattern for the deflectometry configuration. Since the fiducial pattern is based on ideal system geometry, misalignment of the unit under test with its target position causes a discrepancy between the actual image on the camera detector and the ideal fiducial image. We leverage G and C vector polynomials to quantify misalignment and estimate the alignment status through a reverse optimization method. Simulation and experimental results demonstrate that the proposed algorithm can align the 195mm×80mm of a rectangular aperture freeform optic within 10 µm of peak-to-valley accuracy. The computational fiducial-based alignment algorithm is simple to apply and can be an essential procedure for conventional methods of deflectometry system alignment.

Freeform surface selection based on parametric fitness function using modal wavefront fitting.

We present an analytic methodology to guide the selection of a surface within an optical design to apply freeform optimization. The methodology is discussed in the context of other means currently available, such as human intuition, aberration theory, and other direct surface construction methods. We describe the selection criteria for our proposed method and provide the form of the parametric fitness function used to combine the criterion. Finally, a case study comparing a design optimization procedure guided by the proposed methodology to human intuition is presented based on a real instrument designed for a millimeter-wave astronomy application. The methodology is shown to be effective even in the case of an optical system with a large number of freeform/optical surfaces. The proposed approach provides an objective and scalable solution to guide freeform optical system design by aiding a human's design intuition.

Adaptive Shack-Hartmann wavefront sensor accommodating large wavefront variations.

Shack-Hartmann wavefront sensors (SHWFSs) usually have fixed subaperture areas on the detector, in order to fix the minimum and maximum amounts of wavefront departure, or the dynamic range of measurement. We introduce an active approach, named Adaptive Shack Hartmann Wavefront Sensor (A-SHWFS). A-SHWFS is used to reconfigure detection subaperture areas by either blocking or unblocking desired lenslets by using an electronically modulated mask. This mask either increases or decreases the measurable aberration magnitude by placing a liquid crystal display (LCD) panel in front of the lenslet array. Depending on which control signal that is sent to the LCD, the variable, application-dependent blocking pattern (horizontal, vertical, diagonal, uneven) makes this an adaptive and efficient sensor with a variable dynamic range of measurement. This scheme is also useful for regional blocking, which occurs when the wavefront is severely aberrated in a limited region.

Systematic comparison of the use of annular and Zernike circle polynomials for annular wavefronts.

The theory of wavefront analysis of a noncircular wavefront is given and applied for a systematic comparison of the use of annular and Zernike circle polynomials for the analysis of an annular wavefront. It is shown that, unlike the annular coefficients, the circle coefficients generally change as the number of polynomials used in the expansion changes. Although the wavefront fit with a certain number of circle polynomials is identically the same as that with the corresponding annular polynomials, the piston circle coefficient does not represent the mean value of the aberration function, and the sum of the squares of the other coefficients does not yield its variance. The interferometer setting errors of tip, tilt, and defocus from a four-circle-polynomial expansion are the same as those from the annular-polynomial expansion. However, if these errors are obtained from, say, an 11-circle-polynomial expansion, and are removed from the aberration function, wrong polishing will result by zeroing out the residual aberration function. If the common practice of defining the center of an interferogram and drawing a circle around it is followed, then the circle coefficients of a noncircular interferogram do not yield a correct representation of the aberration function. Moreover, in this case, some of the higher-order coefficients of aberrations that are nonexistent in the aberration function are also nonzero. Finally, the circle coefficients, however obtained, do not represent coefficients of the balanced aberrations for an annular pupil. The various results are illustrated analytically and numerically by considering an annular Seidel aberration function.