Abstract. Thermophilic bacteria producing chitinase were collected from Prataan hot spring, East Java, Indonesia and screened. The isolated bacterium was analyzed using 16S rRNA gene sequencing analysis and identified as Paenibacillus sp. The molecular identification was confirmed through morphological and physiological analyses. The production of chitinase was conducted at various incubation times, temperatures, pH and concentrations of colloidal chitin. The optimum condition of the isolate to produce the highest chitinase was 0.9% (w/v) of colloidal chitin (pH 7.0) at 48 °C for 24 hours. The obtained chitinases were optimally active at 55 °C and pH 6.0-7.0. The chitinases were gradually purified by ammonium sulfate precipitation, Sephadex G-100 gel filtration, followed by DEAE-cellulose ion exchange chromatography (IEC). The purification method gave a purification factor of 9.43 and a yield of 2.68%. Two protein fractions were obtained from sodium dodecyl sulfatepolyacrylamide gel electrophoresis (SDS-PAGE) with molecular weights of 68 and 82 kDa.

Abstract- Starch-degrading enzymes not only can be found in bacteria and fungi, but also in plants. Some plants that produce starch-degrading enzymes are germinated grain of sorghum, maize, and mung bean. pH and temperature are factors that can affect the activity of enzyme. Effect of pH and temperature to starch-degrading enzyme activity of these 3 cereal grains are reported in this research. Grain of sorghum, maize, and mung bean were germinated for 2 days and dried to produce malt. Enzymes from these 3 different malts were extracted using 7 buffers with different pH (4.5, 5, 5.5, 6, 6.5, 7) . Buffer that produced highest enzyme activity based on degradation of starch as a substrate (iodine-starch method) and based on formation of reducing sugars as products (DNS method) would be used for determining the effect of temperatures (20 °C, 30 °C, 40 °C, 50 °C). Effect of pH and temperatures to enzyme activity from 3 different malts tend to be fluctuating. Sorghum malt had the highest enzyme activity per gram malt based on degradation of starch activity test. Estimated enzyme activity of sorghum malt was 103,82 mg.g- 1.min-1. Maize malt had the highest enzyme activity based on formation of reducing sugars activity test. Estimated enzyme activity of maize malt was 13.08 mg.g-1.min-1. Keywords: amylase enzyme, sorghum malt, maize malt, mung bean malt, pH temperature Abstrak- Enzim pemecah pati dapat diperoleh dari tanaman selain dari bakteri dan fungi. Beberapa jenis tanaman yang memiliki enzim pemecah pati adalah biji sorgum, jagung, dan kacang hijau yang berkecambah. pH dan suhu merupakan beberapa faktor yang mempengaruhi aktivitas dari enzim. Pengaruh pH dan suhu terhadap aktivitas enzim amilase dari ketiga jenis biji ini akan diamati dalam penelitian ini. Biji sorgum, jagung, dan kacang hijau dikecambahkan selama 2 hari dan dikeringkan untuk menghasilkan malt. Enzim dari ketiga jenis malt ini akan diekstrak menggunakan 7 buffer pH berbeda yaitu buffer pH 4,5; 5; 5,5; 6; 6,5 dan 7. Buffer yang menghasilkan nilai aktivitas enzim tertinggi berdasarkan degradasi substrat pati (metode pati-iodin) dan berdasarkan pembentukan produk gula reduksi (metode DNS) akan digunakan lebih lanjut untuk melihat pengaruh suhu yaitu suhu 20 °C, 30 °C, 40 °C, dan 50 °C. Pengaruh pH dan suhu terhadap aktivitas enzim ketiga jenis malt cenderung fluktuatif. Malt sorgum memiliki nilai aktivitas enzim per gram malt tertinggi berdasarkan uji aktivitas degradasi substrat pati (metode pati-iodin) yaitu 103,82 mg.g-1.min-1 dan malt jagung memiliki nilai aktivitas enzim per gram malt tertinggi berdasarkan uji aktivitas pembentukan gula reduksi (metode DNS) yaitu 13,08 mg.g-1.min-1. Kata kunci: amylase enzyme, sorghum malt, maize malt, mung bean malt, pH temperature

Two different process configurations, simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF), were compared for ethanol production from Shorgum bicolor grain. Optimization modeling for glucoamylase and Zymomonas mobilis concentration in both of SSF and SHF were carried out to obtain optimal concentration of ethanol production. The optimum condition was achieved using 0.021 % v/v of glucoamylase and 30.19% v/v of Zymomonas mobilis for SHF. In contrast, the optimum condition for SSF was 0.021 % v/v of glucoamylase and 17.51% v/v of Zymomonas mobilis. The model predicted SHF processing to be superior. The superiority of SHF over SSF was confirmed experimentally, the result showed ethanol yield of SHF was 134.80 g/L and ethanol yield of SSF was 115.66 g/L after 72 hours incubation time. A high similarity was observed between the predicted and experimental results, demonstrating the accuracy of the model.

Entomopathogenic nematodes (EPN) are one of the soil worms that have been widely used as a natural pest control. EPN has its pathogenic capability because of the mutualistic interactions between nematodes and symbiotic bacteria inside the digestive tract of nematodes. Symbiotic bacteria capable of producing exoenzymes that are toxic to insects. The isolation of symbiotic bacteria accomplished by infection of obtained EPN (Belik II isolate) into Tenebrio molitor larvae. Symbiotic bacteria were isolated from the hemolymph of dead larvae on NBTA media. Isolation of symbiotic bacteria was successfully obtained two morphologically distinct bacteria: B 3.1 isolate and B 4 isolate. Both bacteria were further identified using PCR analysis of the 16S rRNA gene. Based on the sequencing results, the B 3.1 isolate was in accordance with Acinetobacter pittii strain ATCC 19004, while B 4 isolate was in accordance with bacteria Enterobacter aerogenes strain KCTC 2190. The characterization of B 3.1 isolate was shown to have similarities with Acinetobacter sp., i.e.: gram-negative, non - motile, rod-shaped, and some other characteristics of biochemical tests. While the characterization of B 4 isolate was shown to have similarities with E. aerogenes i.e.: gram-negative, rod-shaped, motile, and some other characteristics of biochemical tests. These findings will be the potential to be applied as biological agents in pest control.

Preferensi konsumen terhadap sebuah produk perlu diperhatikan khususnya untuk produk yang masih jarang beredar di masyarakat seperti kefir air (water kefir). Pada penelitian ini, pembuatan water kefirmenggunakan bahan dasar berupa serbuk ashitaba (Angelica keiskei). Tanaman ashitaba banyak dibudidayakan di Indonesia namun sedikit pemanfaatannya. Ashitaba memiliki banyak manfaat seperti antihipertensi, antistroke, dan kaya akan antioksidan. Penelitian ini bertujuan untuk mengetahui faktor penting penentu preferensi konsumen terhadap water kefir teh ashitaba menggunakan kuesioner daring dengan metode Principal Component Analysis (PCA) serta mengetahui pengaruh dari variasi konsentrasi serbuk ashitaba dan lama perebusan terhadap aktivitas antioksidan water kefir teh ashitaba. Hasil analisis dengan metode PCA didapatkan beberapa faktor, dari faktor yang terpenting hingga faktor yang dianggap kurang penting bagi konsumen dalam membuat keputusan untuk membeli water kefir teh ashitaba. Faktor-faktor tersebut adalah aktivitas antioksidan, kandungan vitamin C, dan total bakteri asam laktat dengan skor berturut-turut 0,854; 0,816; dan 0,778. Penelitian ini juga dilakukan untuk mengetahui pengaruh dari konsentrasi serbuk teh ashitaba (5 dan 10%) dan lama perebusan (2, 5, dan 8 menit) terhadap aktivitas antioksidan dari water kefir teh ashitaba. Hasil uji aktivitas antioksidan yang didapat dari nilai inhibisi terhadap DPPH yaitu sebesar 55,57±0,56% didapat dari konsentrasi serbuk teh ashitaba 10% b/v dan lama perebusan 8 menit.