Judul: Peptides Hydrolysate Derived from Collagen of Snakehead Murrel (Channa striata) Skin Demonstrate Anti-oxidant and Anti-cholesterol Activities.
Abstrak: Anti-cholesterol and anti-oxidant play crucial role to combat cardiovascular disease (CVD) related to formation of arterial plagues from oxidation of cholesterol. In the past decades, research on bioactive peptides demonstrating anti-cholesterol and anti-oxidant activities have been reported as the alternative drugs. In this study, acid soluble collagen was extracted from the skin of snakehead murrel and employed to induce production of collagenase by Bacillus licheniformis F11.4. The collagenases secreted were in turn purified through AKTA Purifier (ion exchange, DEAE column) and used to produce peptides hydrolysate. The purified enzymes were grouped in two distinct collagenase fractions, designated as fraction D and F. Peptides hydrolysate produced by the fraction D was found to demonstrate HMG-CoA inhibitor activity comparable to pravastatin and limited anti-oxidant activity. Meanwhile, peptides hydrolysate generated using the fraction F demonstrated anti-oxidant activity comparable to BHT (2mM), vitamin C (2mM) and vitamin E (2mM), but limited HMG-CoA activity. Combination of the fraction D and F resulted in substantial HMG-CoA inhibition and anti-oxidant activities.
Keyword: Anti-cholesterol, anti-oxidant, bioactive peptide, collagen, collagenase, snakehead murrel

Judul: Produksi Batch dan Kontinu Peptida Bioaktif dari Ikan Gabus
Abstrak: There is a high demand for functional foods. Bioactive peptides are potential ingredients in functional food development due to their functional properties, such as antioxidant activity. Snakehead fish (Channa striata) extract (SHFE) is a suitable source of parent proteins for producing bioactive peptides due to its high protein content and hydrophobic peptides. This study aimed to investigate the batch and continuous processes for producing SHFE-based bioactive peptides. Proteases such as Alcalase and Neutrase were used to hydrolyze the parent proteins. The enzymatic membrane reactor facilitated the continuous production of bioactive peptides from SHFE. Bioactive peptides from SHFE that exhibit antioxidant activity can be produced through enzymatic hydrolysis using Alcalase and Neutrase, either in a batch or continuous process. A substrate concentration of 3%, and enzyme-to-substrate ratio of 10%, using Alcalase were selected as the optimum conditions based on their antioxidant activity measured by DPPH and FRAP methods. Based on the calculated fouling rate of continuous operation under the obtained optimum conditions, the production of SHFE-based peptides has the potential to be performed continuously in the long term. Permeate filtration using a 2-kDa membrane increased the antioxidant activity, as indicated by a smaller DPPH IC50 value (i.e., 0.23 mg protein/ml). Further research is needed to identify the specific peptide sequences responsible for antioxidant activity and other bioactivities that might be exhibited by the SHFE-based bioactive peptides. This study is expected to increase the production of functional ingredients from snakehead fish.
Keyword: antioxidant, bioactive peptides, enzymatic membrane reactor, snakehead fish

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
Keyword: