Proteolytic Activity of Silkworm Thorn (Cudrania tricuspidata) Fruit for Enzymatic Hydrolysis of Food Proteins.

This study aimed to isolate the proteolytic fraction from the silkworm thorn fruit (Cudrania tricuspidata) through ethanol precipitation at different ratios, and to determine its proteolytic activity and optimal activity conditions. Furthermore, the hydrolysis characteristics and antioxidant activity of soy protein isolate (SPI) and whey protein concentrate (WPC) hydrolyzates obtained through the enzymatic hydrolysis of freeze-dried silkworm thorn fruit powder (SF) were evaluated. For isolation and partial purification of proteolytic fraction, the water-solubilized fraction of the silkworm thorn fruit was purified through ethanol precipitation at four different ratios of 1:1, 1:2, 1:4, and 1:6 (v/v). The protein recovery rate, caseinolytic activity, protein pattern, and optimal activity (pH, temperature, and inhibitors) of fractional ethanol precipitate obtained from the silkworm thorn fruit (ESF) were evaluated. The proteolytic fraction obtained from silkworm thorn fruit exhibited a major protein band around 65-70 kDa and showed the highest proteolytic activity at a 1:4 ratio of ethanol precipitation (p < 0.05). The optimal activity of the measured enzyme fraction was determined to be at pH 9.0 and 50 °C, and the proteolytic activity of ESF was almost inhibited by phenyl methyl sulphonyl fluoride (PMSF, 2 mM), a serine protease inhibitor. Compared to Alcalase and papain, extensively used as commercial enzymes, the silkworm thorn fruit powder was less effective in hydrolyzing SPI and WPC. Nevertheless, SPI and WPC hydrolyzates mediated with silkworm thorn fruit powder showed even better antioxidant activities than those mediated with Alcalase and papain. Thus, our results show the potential application of silkworm thorn fruit as a novel source of plant protease for producing human-grade protein hydrolyzates.

Synthesis and characterization of new donor-acceptor type copolymers based on fluorene derivatives for photovoltaic solar cells.

In this paper, we demonstrated the successful synthesis of newly designed copolymers, C1 and C2, with donor-acceptor type structure. Both C1 and C2 copolymers contained 9,9-dioctylfluorene-2,7-bis(trimethyleneboronate) as one constructional unit to improve the solubility in common organic solvents. The other constructional unit was 2,3-bis(5-bromothiophen-2-yl)acrylonitrile (DTDBAL) for C1, while 4,7-dibromobenzo[c][1,2,5]thiadiazole unit, 5,5'-dibromo-2,2'-bithiophene unit and N1, N1-bis(4-bromophenyl)-N4,N4-bis(4-(2-phenylpropan-2-yl)phenyl)benzene-1,4-diamine are for C2. We fabricated photovoltaic devices based on the C1 and the C2 copolymers with Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) layer, PC70BM layer, TiOx layer, and aluminum (Al) electrode. The bulk heterojuntion photovoltaic devices using these copolymers as electron donor and PC70BM as the acceptor exhibited good device performances when measured at 100 mW cm-2. The power conversion efficiency (PCE) of the C1 device reached 0.45% with Voc, Jsc and FF of 0.51, 2.50 and 35%, respectively. The PCE of the C2 device reached 0.34% with Voc, Jsc, and FF of 0.56, 2.01 and 30%, respectively.