Sources of antioxidants are abundant in nature, one of which is derived from microalgae. Microalgae species that have potentially to be developed as a producer of antioxidant compounds is Porphyridium cruentum (S. F. Gray) Nägeli. P. cruentum is a red microalga (Rhodophyceae) and has been known as polysaccharides producer (exopolysaccharide and endopolysaccharide) and as an antioxidant. This study aims to determine antioxidant activity of the extracts and biological toxicity of endo-and exopolysaccharide P. cruentum. The antioxidant activity use reduction method of free radicals (DPPH), whereas toxicity uses Brine Shrimp Lethality Test. (BSLT). The result shows that there is an antioxidant activity with IC 50 value of 50.586 5 mg ⋅ kg −1 (exopolysaccharide) and 145.998 8 mg ⋅ kg −1 (endopolysaccharide). In addition, the result indicates the toxic nature of the Artemia salina Leach. with LC 50 values of 513.175 1 mg ⋅ kg −1 (exopolysaccharide) and 521.823 3 mg ⋅ kg −1 (endopolysaccharide).Therefore, endo-and exopolysaccharide produced by P. cruentum suitable to be used as an alternative source of natural antioxidants and potential for further developed as antitumor drugs.
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.
The objective of this research was to know the antibacterial activity from the Porphyridium cruentum. P. cruentum is the Rhodophyceae algae. The extraction of microalgae biomass used dichloromethane solution and resulted three types extracts. Antibacterial activity of the extracts using the clear zone method to Escherichia coli, Bacillus subtilis and Staphylococcus aureus bacteria. Identification of antibacterial substance of the extracts were using Gas Chromatograph Mass Spectrophotometer (GCMS). The results showed that C type extract have antibacterial activity to all of indicator bacteria, neither do A type extract. Whereas the B type extract inhibited to B. subtilis and S. aureus growth. Analysis of the antibacterial compound by GC-MS was fatty acid. The major component of antibacterial from the P. cruentum was metil hexadecanoate acid (palmitic acid), the percent area was 41,15 % of B type extract and 60,36 % of C type extract.
HIDROLISIS BIOMASSA MIKROALGA Porphyridium cruentum MENGGUNAKAN ASAM (H2SO4 dan HNO3) DALAM PRODUKSI BIOETANOL. Porphyridium cruentum ada salah satu jenis mikroalga uniseluler dari kelas Rhodophyceae yang memiliki karbohidrat. Kandungan karbohidratnya yang tinggi, sehingga mikroalga ini berpotensi sebagai sumber bioetanol. Penelitian ini bertujuan untuk mengetahui proses hidrolisis biomasa P. cruentum menggunakan asam untuk menghasilkan bioetanol. Biomassa P. cruentum dihidrolisis dengan menggunakan 2 jenis asam yaitu HNO3 dan H2SO4. Variasi konsentrasi asam yang digunakan adalah 1%; 2% dan 3%, pada suhu 100 o C selama 60 menit. Fermentasi dilakukan selama 5 hari dengan menggunakan Saccharomyces cerevisiae. Analisis karbohidrat menggunakan metoda fenol sulfat, gula pereduksi menggunakan metoda DNS, sedangkan analisis kadar etanol menggunakan High-Performance Liquid Chromatography (HPLC). Hasil dari studi ini, kandungan karbohidrat P. cruentum diperoleh sebesar 22,82%. Semakin tinggi konsentrasi asam yang digunakan, semakin tinggi pula kadar gula reduksi yang diperoleh. Kadar etanol dari biomasa yang dihidrolisis menggunakan H2SO4 maksimum dicapai pada konsentrasi 1% H2SO4 yaitu 34,5% dan dicapai pada hari ke-4, sedangkan biomassa yang dihidrolisis dengan HNO3 maksimum dicapai pada konsentrasi 2% yaitu sebesar 14,83% pada hari ke-2. Penggunaan konsentrasi asam yang rendah dapat mengurangi efek negatif terhadap lingkungan. Mikroalga P. cruentum yang mengandung karbohidrat 22,82% dapat dijadikan sebagai salah satu bahan baku untuk menghasilkan bioetanol yang berkelanjutan.
Microbial infection by bacteria has caused severe health problems worldwide. Treatment with antibiotics as the current solution has several drawbacks and triggers the phenomenon of bacterial resistance. Therefore, there is an urgency to look for a natural antimicrobial that is safer and has fewer side effects. One of the most promising antibacterial agents is Spirulina platensis. This research was conducted to evaluate the antibacterial activity of microalgae S. platensis against Propionibacterium acne, Staphylococcus epidermidis, and Enterobacter aerogenes and identify compounds from the active fraction of microalgae. Biomass was extracted with ethanol 96% using the reflux method then partitioned with immiscible solvents such as hexane, ethyl acetate, and water. Partial purification was carried out by chromatography techniques such as thin-layer chromatography and column chromatography. The compounds of active fractions were identified by GC-MS analysis. The result showed that ethyl acetate extract had vigorous antibacterial activity against all tested bacteria. The highest activity (14.4 ± 0.63 mm and 16.9 ± 1.48 mm) was achieved against P. acne; followed by S. epidermidis (13.05± 0.14 mm and 13.15 ± 0.0 mm), and E. aerogenes (11.7 ± 2.05 mm and 12.6 ± 1.90 mm), at concentrations 20,000 ppm and 30,000 ppm, respectively. The results indicated that the extract is more sensitive to Gram-positive bacteria (P. acne and S. epidermidis) than Gram-negative bacteria (E. aerogenes). Purification of the extract resulted in fraction 2 and fraction 6 as the most potential fractions for further analysis and identification. Based on the antibacterial activity, inhibition zones of fractions are wider than extracts. It could be assumed that the purification process enhances the activity of a sample. GC-MS analysis revealed that the dominant compounds of fractions 2 and 6 were bis (2-ethylhexyl) phthalate (67.76%) and 1,2-Benzendicarboxilic acid, bis (2-ethylhexyl) ester (50,88%), respectively. This result indicated that the ethyl acetate fraction of the microalgae S. platensis has the potential as a natural antibacterial.
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