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Soy protein recovery from hexane-defatted soybean flakes using conventional methods is generally low. Importantly, some tightly-bound sugar in the soy flakes ends up in soy protein, thereby deteriorating the usefulness and quality of soy protein as a food ingredient. This research investigated the use of high-power ultrasound prior to soy protein extraction to simultaneously enhance protein yield and facilitate more sugar release in soy whey. The nutrient-rich soy whey was then used as a cheap growth medium to produce high-value nisin using Lactococcus lactis subsp. lactis. A nisin sensitive organism Micrococcus luteus was used as an indicator organism for international unit determination of nisin production as compared to standard. Soy flakes and water was mixed at the ratio of 1:10 (w/w). The slurry was then sonicated for 15, 30, 60 and 120 sec at a frequency of 20 kHz. The ultrasonic amplitude was maintained at 84 µmpp (peak to peak amplitude in µm) for all sonication durations. The results showed that with ultrasound pretreatment, the protein yield improved as much as by 46% in soy extract and sugar release by 50% with respect to nonsonicated samples (control). To maximize nisin production from soy whey, different parameters, such as aeration/agitation and incubation period were optimized. Nisin production from standard medium, DeMan, Rogosa and Sharpe (MRS) and soy whey was tested and compared. Maximum nisin production was achieved in stationary conditions and showed a continuous increase in yield till 48h of incubation (incubation period beyond that was not tested). Maximum nisin yield of 1.78 g/L of soy whey was obtained at 30°C and pH of 4.5 as opposed to 2.96 g/L of nisin with MRS medium

Dry grind corn milling does not reach full efficiency of starch conversion to sugars and subsequently to ethanol because of limitations in the milling process. This paper examines the use of high-power ultrasonics to enhance the release of fermentable sugars from milled dry corn. In this work, 20 kHz ultrasonic energy was used to pretreat corn mash prior to enzymatic conversion of corn starch to glucose in a batch-mode. The ultrasonic amplitude was varied from 0, 191 to 320 µmpp. The corn mash was sonicated for 0 (control), 20 and 40 seconds. Other experimental variables that were studied included the effect of temperature and pretreatment sequencing, e.g., ultrasonic pretreatment before and after enzyme addition. It was found that the reaction rate kinetics of the enzymatic reactions increased threefold for sonicated samples. Energy balance (efficiency) analysis indicated that ultrasound pretreatment released twice as much energy (as sugar) when introduced during pretreatment. Based on scanning electron microscopy examination and particle size analysis, the enhancement of the conversion was primarily attributed to particle size reduction, resulting in an increase in the surface area to volume ratio, which in turn increased the available enzymatic reaction sites. One of the most striking findings was that enzymes were not degraded by low level ultrasonication. In addition, the most significant increase in sugar yield was seen when the enzymes were added before ultrasonic pretreatment. Ultrasound has the potential to enhance the ethanol yield from cornstarch and reduce the production cost significantly in commercial dry corn milling ethanol plants.

Conventional dry-grind corn ethanol plants generate considerable amounts of low-value thin stillage. Thin stillage is currently concentrated by flash evaporation, an energy-intensive process, to produce syrup, which is blended with distillers dried grains (DDG) to produce DDGS. The condensate is recycled as process water. Thin stillage is generated in pasteurized condition and is rich in organic compounds and other nutrients, with a chemical oxygen demand (COD) of 90 g/L. The low initial pH of 4 and high nutrient levels make it an ideal medium for fungal cultivation. In this research, the fungus Rhizopus oligosporus was cultivated on thin stillage obtained from a local dry-grind ethanol plant. Preliminary batch tests in a 1.75-L reactor showed proliferous fungal growth under non-sterile conditions and COD removal of up to 86%. Suspended solids decreased from an initial 2 to 3% to as low as 0.03%, with partial removal by attachment to the fungal biomass. The effluent was well-clarified with a light yellow tint. Solids separation is very important, and the effluent from the fungal process could potentially be recycled as process water with minimal further treatment. The fungal biomass is high in lysine (corn protein is low) making it a nutritionally beneficial livestock feed; if fungal cell walls are disrupted, it can be co-fed with DDG to monogastrics. The ability to feed more of the byproducts to hogs and chickens would help resolve the anticipated corn grain shortfall created by the booming ethanol industry. The fungal biomass could also be used to extract chitin/chitosan.