AbstrakPenelitian ini bertujuan untuk mengetahui pengaruh pH dan suhu dalam pembentukan N-Asetilglukosamin (NAG) dari kitin cangkang udang oleh Serratia marcescens PT-6 yang difermentasi dalam media kitin cair. Parameter yang diuji dalam proses pembentukan NAG meliputi pertumbuhan bakteri, aktivitas kitinase (U/ml), serta konsentrasi NAG dalam medium (mg/ml). Pertumbuhan bakteri diukur berdasarkan kekeruhan (OD 600 ), sedangkan aktivitas kitinase dan konsentrasi NAG dalam medium dianalisis secara kuantitatif dengan metode kolorimetri. Variasi nilai pH yang dicobakan dalam media kitin cair adalah pH 5; 6; 7; 8, sedangkan variasi suhu yang dicobakan adalah 30°C; 37°C; dan 40°C. Hasil penelitian menunjukkan bahwa konsentrasi NAG maksimum yang dihasilkan oleh Serratia marcescens PT-6 sebesar 33,86 µg/ml pada hari ke-3 inkubasi, dengan kondisi pH 7 dan suhu 30°C. Aktivitas kitinase pada waktu yang sama mencapai nilai maksimum sebesar 0,002 U/ ml, sedangkan nilai OD 600 sebesar 0,42 menunjukkan bakteri berada pada fase logaritmik. Hasil penelitian ini menunjukkan bahwa Serratia marcescens PT-6 berpotensi untuk dikembangkan lebih lanjut dalam proses biokonversi NAG dari limbah cangkang udang secara enzimatis dengan memperhatikan kondisi kulturnya. Kata kunci: Kitinase, kitin, N-Asetilglukosamin, Serratia marcescens PT-6 AbstractThe study aimed to determine the effect of pH and temperature on N-Acetylglucosamine (NAG) formation from shrimp shell chitin by Serratia marcescens PT-6 fermented in chitin broth medium. Parameters examined on NAG formation include bacteria growth, chitinase activity (U/ml), and NAG concentration in medium (mg/ ml). Bacteria growth was measured by turbidity (OD 600 ), while chitinase activity and NAG concentration in the medium were analyzed quantitatively by colorimetric assay. The variation of initial pH examined in chitin broth medium was 5; 6; 7; 8, while temperature variation was 30°C; 37°C; dan 40°C. The results show that maximum concentration of NAG formed by Serratia marcescens PT-6 was 33.86 µg/ml on day-3 of fermentation, at pH 7 and temperature of 30°C. Chitinase activity on the same day was 0.002 U/ml, while OD 600 value of the culture was 0.42 indicating the bacteria were in the log phase. This research implies that Serratia marcescens PT-6 is potential to be optimized further for the bioconversion process of NAG from shrimp shell waste through an enzymatic method by modifying its culture condition.

Chitin hydrolysate is one of the value added product derived from shrimp shell waste. Production of chitin hydrolysate using biological process offers an environmental friendly method compared to chemical process. Serratia marcescens PT-6, a gram negative chitinolytic bacterium isolated from shrimp pond sediment, shows good activity in hydrolyzing chitin. This study aimed to improve the chitinase activity of S. marcescens PT-6 culture by optimizing the component of chitin-containing medium (additional nitrogen source, additional carbon source, and colloidal chitin). The optimization of chitinase by S. marcescens PT-6 culture was done using one variable at a time method. The sequence of the research were to optimize 1) the type of additional carbon source (glucose, lactose, sucrose, and starch), 2) the type of additional nitrogen source (yeast extract, peptone, ammonium sulphate, and ammonium chloride), 3) the concentration of colloidal chitin (0.5; 1; 1.5; 2; and 2.5%), and 4) the concentration of the additional carbon and nitrogen source. The culture of S. marcescens PT-6 was incubated in colloidal chitin medium at 30 o C and chitinase activity from culture supernatant was analyzed. The results showed that starch gave the highest chitinase activity compare to other carbon source, meanwhile yeast extract was chosen as the best nitrogen source among others. The combination of 1.5% colloidal chitin with 0.5% starch and 0.1% yeast extract in medium increased the chitinase activity of S. marcescens PT-6 to 0.021 U/ml. These results indicated that an appropriate medium composition could increase the chitinase activity produced by S. marcescens PT-6 culture.