Scenedesmus sp. has tremendous potential to produce bioethanol due to its high content of carbohydrate, approximately 10-52%. This study aimed to investigate the effect of hydrolysis time and acid concentration on ethanol production fermented by Saccharomyces cerevisiae. The analysis included in this research were cell density calculation, pH level, carbohydrate content, reducing sugar content, and ethanol content tested by Gas Chromatography. Biomass of Scenedesmus sp. was hydrolyzed using 1%, 2%, and 3% sulfuric acid for 75 minutes and 105 minutes. The hydrolysate was adjusted its pH to 4-5 using NaOH 50% then it was added with nutrients. The fermentation process was carried out for 5 days and samples were collected every day. The results showed that the highest ethanol content was 1.1 % and achieved on the 1st day of fermentation with 75 minutes of hydrolysis process using 3% sulfuric acid. It was followed by a 105 minutes hydrolysis process using 3% sulfuric acid which yielded a value of 1.095% on the 2nd day of fermentation. Optimization of the hydrolysis and fermentation process are needed for a further study to obtain high ethanol content.

ABSTRAK.Fikobiliprotein merupakan kompleks pigmen-protein yang dimiliki oleh sianobakteria dan menunjukkan berbagai aktivitas biologi yang luas. Penelitian ini bertujuan untuk mengetahui aktivitas antioksidan dan toksisitas hayati dari pigmen fikobiliprotein Chroococcus turgidus yang diekstrak menggunakan berbagai pelarut polar, yaitu air, kalsium klorida dan buffer fosfat. Uji aktivitas antioksidan dilakukan dengan metode perendaman radikal bebas DPPH sedangkan uji toksisitas hayati dengan BSLT. Hasil penelitian menunjukkan bahwa pigmen fikobiliprotein berhasil diekstraksi menggunakan ketiga macam pelarut. Hasil terbaik dicapai oleh pelarut air dengan kadar pigmen 0,296 mg/mL. Berdasarkan uji aktivitas, pigmen fikobiliprotein yang diekstrak menggunakan pelarut air bersifat aktif sebagai antioksidan dengan nilai IC 50 sebesar 198,706 µg/mL, sedangkan hasil ekstraksi menggunakan kalsium klorida dan buffer fosfat tidak aktif sebagai antioksidan dengan nilai IC 50 berturut-turut adalah 1255,430 µg/mL dan 1508,130 µg/mL. Hasil uji toksisitas menunjukkan pigmen fikobiliprotein yang diekstrak menggunakan air tidak bersifat toksik dengan nilai LC 50 sebesar 1920,430 µg/mL sedangkan pigmen yang diekstrak menggunakan kalsium klorida dan buffer fosfat bersifat toksik dengan nilai LC 50 berturut-turut sebesar 534,070 µg/mL dan 221,050 µg/mL. Hasil penelitian ini membuktikan bahwa pigmen fikobiliprotein sianobakteria C. turgidus dapat dimanfaatkan sebagai antioksidan alami. Aktivitas toksisitas yang dimilikinya memberikan gambaran untuk pengujian lebih lanjut ke arah potensi dan seleksi senyawa antikanker.

Microalgae, mainly green algae, are well known as sources of lipids for food, feed, and energy. As our institution owned microalgae collections, we performed microalgae screening to find candidate/s, producing high lipid content. In this research, microalgae were screened by various media, and then the medium was optimized. Larger scale cultivation was done in order to find out the yield of the biomass production and lipid content. The condition with phosphate buffer was applied to increase the lipid accumulation. The lipid content was analyzed by Nile red staining. As a result, Chlamydomonas reinhardtii and Chlorella vulgaris showed high biomass production in the Tris-Acetate-Phosphate (TAP) medium. Chlamydomonas reinhardtii at four times concentration and C. vulgaris at the initial concentration of TAP medium demonstrated the most increased biomass production. The maximum biomass production and lipid content was 0.9 g/l and 31% for C. reinhardtii and 1.7 g/l and 27% for C. vulgaris, respectively. Under starvation, the lipid content was increased up to 52% for C. reinhardtii and 34% for C. vulgaris, which were higher than their control. From this study, the TAP medium was found to have the most increased biomass production, and starvation enhanced lipid accumulation.

Chlorella is widely used for its fast growth rate and easy cultivation with 14–30% lipid content and 36–59% dry weight. Thus, sodium hydroxide is used to increase carbon consumption, biomass, and metabolites productions in microalgae. This study was conducted to observe the effect of sodium hydroxide addition on biomass and metabolites  production in photoautotrophic cultivated Chlorella sorokiniana. Microalgae C.sorokiniana (LIPI12-Al016) was obtained from the culture collection of Microalgae and Bioprocess Engineering Research Group laboratory, National Research and Innovation Agency. Then, the microalgae were cultivated in media with various concentrations of sodium hydroxide. Biomass production was measured by gravimetry, and carbon consumption was measured by acid-alkalimetry. Sodium hydroxide 60 mM gave the best growth, maximizing average carbon consumption to 691.8 mg.L-1 and biomass production to 598.3 mg.L-1. The utilization of NaOH in the medium did not increase the metabolites content, except for protein. Carbohydrate was the dominant metabolite among the others. Fatty acids profile mainly composed of C16 and C18 fatty acids, which are favorable for biodiesel production. These results gave an overview of the potency of microalgae C. sorokiniana as a CO2 mitigation agent and alternative sources of energy and nutrition.