Though top executive turnover's economic consequence is highlighted in earlier studies, its link with innovation behaviour has remained relatively underexplored. This study aims to fill this gap through investigating whether, and if so, how, top executive turnover event influences firms' R&D investment. Based on a sample of 2,810 A-share listed companies in China for the period 2008-2016, our results suggest that top executive turnover is negatively related to enterprises' R&D investment. This is mainly because top executive turnover increases the departure rate of R&D personnel, which worsens enterprises' internal R&D environment. The findings also indicate that the negative effect of top executive turnover on R&D investment is accentuated for family enterprises and non-stateowned corporations. Our results have implications for the literature on top executive turnover and enterprises' innovation behaviour and can inform practice, particularly with respect to the selection of top management team members.
This work established an integrated utilization of dairy whey in β-galactosidase production from Lactobacillus bulgaricus and prebiotics synthesis by the probiotic enzyme. A cost-effective whey-based medium was newly developed for culturing Lactobacillus bulgaricus to produce β-galactosidase. The medium was optimized through response surface methodology (RSM) involving a series of statistical designs, such as the Plackett–Burman design, steepest ascent experiment, and central composite design. Under the optimized medium, the β-galactosidase activity of L. bulgaricus reached 2034 U/L, which was twice that produced from the traditional MRS medium. The cells of L. bulgaricus harvested from the whey-based medium were subsequently treated with lysozyme. The resulting crude enzyme was used as an efficient catalyst, which catalyzed the synthesis of the prebiotic galacto-oligosaccharides (GOS) in a high yield of 44.7% by using whey (200 g/L) as the substrate. The sugar mixture was further purified by activated charcoal adsorption, thereby yielding a high-purity level of 77.6% GOS.
This study aims to discover natural bioactive substances as alternative therapies to current medical and surgical treatments for osteoarthritis (OA). Chicken cartilage hydrolysate (CCH) was produced using trypsin and separated via ultrafiltration into CCH-I (molecular weight (MW) > 10 kDa) and CCH-II (MW <10 kDa). Results showed that CCH and its fractions (CCH-I and CCH-II) could relieve OA with different extents, and the outcome using these treatments depended on their especial composition. CCH-II (a fraction rich in low MW peptides with no chondroitin sulphate (CS) and low in sugar) exhibited desired OA-alleviating effect in papain-induced rat and highest in vitro antioxidant activities. CCH-I (a fraction rich in CS and in high MW peptides) might have an adverse effect on renal function. Therefore, it is industrially feasible to produce anti-inflammatory and antioxidative CCH, especially CCH-II, with the therapeutic potential for alleviating or treating OA. Further separation of CS from CCH-I may lead to a commercial pure CS product for treating OA.
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