Search

Efforts to reduce organic sulfur in coal are taken through biodesulfurization by using desulfurization bacteria to release covalently-bound sulfur from the coal matrix. Coal is a complex hydrocarbon material that requires collaboration from more than one type of bacteria in a consortium for desulfurization. The current study shows how the individual members of a bacterial consortium obtained directly from coal samples grew on the coal. Mineral medium containing sub-bituminous coal with a concentration of 10%, 15%, and 20% served as a carbon source and the only sulfur to support the consortium's growth. The examination included growth patterns, concentrations of dibenzothiophene as an organic sulfur representative, pH, and sulfate concentration as the sulfur product released into the medium. The growth of individual members of the consortium was observed for 336 h. The consortium grew in all three coal concentrations with slightly different cell growth patterns and the release of dibenzothiophene. Members of the consortium grew alternately and overlapped, which showed possible linkages or dependence on products and existence from the growth of other members. The existence of the primary strain Moraxella osloensis COK1 indicated that they played a role in the activities and growth of other members. The alternating growth is discussed to produce a hypothetical illustration of how several other members play in using sulfur in a well-known desulfurization pathway. In conclusion, this study provides a deeper insight into the value of consortium members individually but growing together while swarming coal as a complex resource to become low-sulfur coal.

Tempeh is a fermented food ingredient from soybeans that uses various Rhizopus molds, such as Rhizopus oligosporus, Rhizopus oryzae, Rhizophus stolonifer. In this study, the preparation of tempe using mixed culture was carried out in the ratio of Rhizopus oryzae, Rhizopus oligosporus, Rhizopus stolonifer inoculums, namely 1: 1: 1; 1: 2: 1; 2: 1: 2; 1: 1: 2; 2: 1: 1; market yeast "Raprima", produces the characteristics of tempe according to SNI 01-3144-2009, formation of Vitamin B12, Folate and Isoflavones as well as pH, and Total Bacteria. The content of vitamin B12 was obtained in yeast "raprima" of 0.013 g / 50g of tempeh while tempeh made with pure inoculums of Rhizopus sp did not contain vitamin B12 or folic acid, pH value of 4.2 and total bacteria 14.3x108 cfu / ml and organoleptic reception. Tempe 1: 2: 1 has the characteristics of color, aroma, taste, texture and viscosity acceptable to the panelists.

Biosurfactant is a microbial bioproduct that is used to reduce the surface tension, and can acted as emulsifier, dispersant, and anti-adhesive. Optimization of biosurfactant production needs to be done, not only to increase its production quantity, but also to reduce overall production cost. This study aims to determine the most suitable and optimum concentration of nitrogen source for biosurfactant production and its preservation techniques. The biosurfactant was produced by Pseudoxanthomonas sp. G3 using minimal salt medium with 2% light crude oil as carbon source and different nitrogen sources in the form of urea, sodium nitrate, and ammonium nitrate. The activity of biosurfactants were measured by emulsification index (E24), interfacial tense (IFT), oil drop assay, and dry weight. Potassium sorbate 0.2% (w/v) was used as preservative agent. The results showed that biosurfactant production using sodium nitrate as a nitrogen source provides the highest activity and yield. The E24 value was 76.63% and the clear zone diameter observed was 0.875 cm. The overall decreased in IFT was 35.4% and the biosurfactant dry weight was 0.45 gL-1. Microbial contamination occurred after 3 weeks of storage in the treatment without the addition of preservative. It also showed that the activity of biosurfactants (emulsification and IFT) were gradually decreased during storage. In conclusion, the optimum biosurfactant production by Pseudoxanthomonas sp. G3 was obtained by the addition of sodium nitrate 0.3% (w/v). Meanwhile, the most effective biosurfactant preservation method was by adding potassium sorbate which was stored at 4 ℃.

Microbial enhanced oil recovery (MEOR) is a tertiary oil recovery process which aims to increase the crude oil recovery uptake to 55% from its original oil in place. In its application, indigenous microorganisms are commonly used as the main biological agents, but the isolation processes become more complicated due to environment’s extreme condition. This study aims to determine the optimum formulation for the enrichment and isolation medium, in order to obtain a highly diverse of indigenous hydrocarbonoclastic bacteria. The isolation process was carried out in two stages; the isolation of mild oil fraction degrading bacteria, and isolation of the heavy oil fraction degrading bacteria which confirmed by the SARA (saturated, aromatic, resinic, and asphaltic) fraction chromatography analysis. Four enrichment and five isolation media were formulated based on the distinction in the macro-and micronutrient composition. Overall, a total of 92 isolates were successfully isolated. The highest bacterial diversities were achieved in the enrichment medium B (crude oil used as carbon source which supplemented with sodium lactate) and isolation medium I (nutrient agar with twice agar concentration), each with 37 and 33% of obtained isolates, respectively. The newly formulated medium can be further utilized to isolate various types of indigenous bacteria from the oil well which were able to degrade SARA fraction from crude oil. The result showed that ABG2-7 as the isolate with the highest activity on SARA degradation. The amount of 15% inoculum of ABG2-7 isolate was able to degrade heavy crude oil, thus might serve as potential bacteria for MEOR application.

Ambonese arrack is one of the traditional fermented beverage product in Maluku, Indonesia. The microbiological research of this beverage that is processed using coconut sap as raw material has never been done before. The research aimed to analyze the microbial succession and chemical characteristics during fermentation of Ambonese arrack. The sample of coconut sap was taken from traditional producer in Mahia village, Ambon. The dominant microbes in the fermentation of Ambonese arrack were Pichia polymorpha and Kloeckera javanica. The highest numbers of these two microbes was obtained after 15 hours fermentation (9.6 log Cfu/mL and 9.9 Cfu/mL, respectively). The sugar content decreased from 593.3 mg/L to 474.3 mg/L, whereas ethanol content increased from 0.0018 g/L to 0.0100 g/L. The pH value decreased from 4.70 to 3.10. The research has isolated indigenous microbes in Ambonese arrack fermentation which was considered as novelty. The bacteria that play a role in fermentation can be used as a starter in the fermentation of various beverage products, especially Ambonese arrack. The results of this research can improve the quality of this fermentation product in the future.

Terasi is a fermented shrimp paste unique to Indonesia and is used in dishes to add umami and saltiness. In a previous study, the controlled fermentation of terasi was optimized using starters containing three bacterial isolates: Staphylococcus saprophyticus, Bacillus subtilis, and Lactobacillus murinus. However, the influence of controlled fermentation using these starters on the metabolites in terasi has not yet been studied.Therefore, this study aimed to investigate the effect of controlled fermentation on taste-related metabolites in terasi using a metabolomics approach.Non-targeted analysis indicated that amino acids contributed to variations during fermentation. Subsequently, targeted analysis of amino acids revealed that terasi subjected to controlled fermentation using a starter with a 2:1:2 ratio of S. saprophyticus, B. subtilis, and L. murinus, respectively, resulted in a product containing D-amino acids, such as D-Asp, D-Gln, and D-Leu that was unique when compared to other terasi products prepared using controlled fermentation. Genetic analysis of isolates from the terasi produced using controlled fermentation was also carried out, and this is the first study to suggest that Staphylococcus spp. has the potential to produce D-amino acids.In conclusion, the ratio of bacterial species in starter cultures used in controlled fermentation influenced the amino acid profile of the product and starters with a higher ratio of Staphylococcus spp. may result in the production of D-amino acids.

Low-salt shrimp paste, or terasi, is an Indonesian fermented food made from planktonic shrimp mixed with a low concentration of salt. Since high daily intake of sodium is deemed unhealthy, reduction of salt content in shrimp paste production is desired. Until now, there is no reported investigation on the bacterial population and metabolite composition of terasi during fermentation. In this study, the bacterial community of terasi was assessed using high-throughput sequencing of the 16S rRNA V3–V4 region. From this analysis, Tetragenococcus, Aloicoccus, Alkalibacillus, Atopostipes, and Alkalibacterium were found to be the dominant bacterial genus in low-salt shrimp paste. GC/MS-based metabolite profiling was also conducted to monitor the metabolite changes during shrimp paste fermentation. Results showed that acetylated amino acids increased, while glutamine levels decreased, during the fermentation of low-salt shrimp paste. At the start of shrimp paste fermentation, Tetragenococcus predominated with histamine and cadaverine accumulation. At the end of fermentation, there was an increase in 4-hydroxyphenyl acetic acid and indole-3-acetic acid levels, as well as the predominance of Atopostipes. Moreover, we found that aspartic acid increased during fermentation. Based on our findings, we recommend that fermentation of low-salt shrimp paste be done for 7 to 21 days, in order to produce shrimp paste that has high nutritional content and reduced health risk.

Biosurfactants are one of the microbial bioproducts that are in most demand from microbial-enhanced oil recovery (MEOR). We isolated and screened potential biosurfactant-producing bacteria, followed by biosurfactant production and characterization, and a simulation of the MEOR application to biosurfactants in a sand-packed column. Isolate screening was conducted based on qualitative (hemolytic blood assay and oil-spreading test) and semi-qualitative (emulsification assay and interfacial tension measurement) parameters. Bacterial identification was performed using 16S rRNA phylogenetic analysis. Sequential isolation yielded 32 bacterial isolates, where Pseudomonas sp. G3 was able to produce the most biosurfactant. Pseudomonas sp. G3 had the highest emulsification activity (Ei = 72.90%) in light crude oil and could reduce the interfacial tension between oil and water from 12.6 to 9.7 dyne/cm with an effective critical-micelle concentration of 0.73 g/L. The Fourier transform infrared spectrum revealed that the biosurfactant produced was a glycolipid compound. A stable emulsion of crude extract and biosurfactant formed at pH 2–12, up to 100 °C, and with a NaCl concentration of up to 10% (w/v) in the response-surface method, based on the Box–Behnken design model. The sand-packed column experiment with biosurfactant resulted in 20% additional oil recovery. Therefore, this bacterium and its biosurfactant show potential and the bacterium is suitable for use in MEOR applications.

Solid-state fermentation is commonly applied to valorize agro-industrial waste to produce various bioproducts. Good solid-state fermentation highly depends on the development of inoculum before the fermentation. The development of inoculum using suitable bacteria and the appropriate age of inoculum may reduce the lag phase and accelerate bacterial growth during fermentation. This chapter describes the solid-state fermentation of agro-industrial wastes using heterofermentative lactic acid bacteria with a focus on the stage of inoculum development, including preparation of medium, activation of bacteria, and growth curve analysis, to determine bacterial growth rate during the fermentation. This process can also be applied to other complex solid substrates.

Previous laboratory studies have shown that the combination of molasses and commercially-available fertilizer (NPK and ((NH4)2HPO4) can stimulate bacterial growth that decreases oil viscosity and interfacial tension (IFT). In this project, a huff-and-puff field implementation of MEOR nutrient injection has been conducted in two selected wells in Bentayan Field, South Sumatera, BN-38, and BN-81. The project objective is to evaluate and analyze the effect of nutrient injection towards oil recovery, changes of indigenous microbes that alter oil characteristics from the two selected wells during three months of post-nutrient injection monitoring phase. Changes of oil production were measured in-line after the gross produced liquid passes through a separator unit. The abundance of aerobic, anaerobic, and sulfate-reducing bacteria (SRB) was examined by using Total Plate Count (TPC) method, while anaerobic bacteria and SRB were cultivated using the Hungate technique. The chemical compositions of the oil were analyzed before and after nutrient injection by using gas chromatography-mass spectrometry (GC-MS) method. Fluid analysis of the oil (kinematic viscosity and interfacial tension) were measured by viscometer and IFT meter. The program of nutrient injection started with 500 bbls of first nutrient injection, followed by 100 bbls of post-flush 1, 500 bbls of second nutrient injection, 100 bbls of post flush 2, soaking for 14 days, 2000 bbls post-flush 3, and soaking for seven days. Based on the results of bacterial abundance analysis for three months, there was an increase of almost 1000-fold of total aerobic bacteria abundance and 10-fold of anaerobic bacteria abundance after nutrient injection. The expansion of bacterial abundance successfully changed the physical-chemical condition of the oil, decreasing oil viscosity by approximately 24% and IFT by 47%. In both wells, water cut values were decreased from 99% to 92%, and incremental oil was gained by 1395 barrels. Huff and puff nutrient injection seems to be low-cost EOR since it can be included in the daily operating cost with the additional cost of workforce, nutrient, monitoring, and analysis. Economic analysis calculation of this project resulted in Pay-out-Time (POT) by four months with an incremental gain of approximately 1750 barrels.

Biostimulation is a method of microbial enhanced oil recovery (MEOR) by injecting nutrients into an oil well to stimulate the growth of indigenous bacteria and their activities dealing with the increasing of oil recovery. This study aimed to obtain an optimum nutrient formulation at laboratory scale to be applied for MEOR field biostimulation pilot project. Field monitoring of chemical and bacterial composition in oil well was also carried out up to twelve weeks after biostimulation. The oil composition was analyzed by GC-MS and column chromatography. Bacterial community analysis was performed using 16S rRNA gene as the biomarker, which was sequenced by Illumina Miseq Sequencing. Based on Response Surface Methodology (RSM), the optimum nutrient concentrations that increase bacterial growth and decrease oil viscosity were molasses 5% (w/v), NPK 0.5% (w/v), and DAP 0.5% (w/v). The relative abundance of the bacteria and the community composition constantly changed during the monitoring process. Injection of molasses stimulated the growth of the hydrocarbonoclastic bacteria until the end of monitoring period.

This study aims to develop a hybrid zero water discharge (ZWD) - recirculating aquaculture system (RAS) system to improve water quality, as well as the growth, survival, and productivity, of the super-intensive white shrimp culture under low salinity conditions at semi-mass and the industrial level. The study consisted of two parts: (1) a semi-mass trial for the optimization of shrimp production using a hybrid ZWD-RAS system with a total volume of 2.7 m3 at the different shrimp stocking densities of 500 PL/m3, 750 PL/m3, and 1,000 PL/m3 and (2) an industrial trial at a commercial shrimp urban farming facility in Gresik, East Java, with total volume of 110 m3 at the optimum shrimp stocking density from the semi-mass trial. Both the semi-mass and industrial trials were performed in five steps: (1) preparation and installation of the RAS and ZWD system components; (2) preparation of microbial components including nitrifying bacteria, the microalgae Chaetoceros muelleri, and the probiotic heterotrophic bacteria Bacillus megaterium; (3) acclimatization of white shrimp post larvae from the salinity level of 32 ppt to 5 ppt; (4) conditioning of the biofilter used in the RAS and shrimp tank (microbial loop manipulation in ZWD); and (5) shrimp grow-out rearing for 84 days and 60 days for the semi-mass trial and the industrial trial, respectively. The hybrid system combined a ZWD system and an RAS. Shrimp tanks were conditioned with the addition of microbial components for ZWD at the beginning of the culture period. The RAS was operated when NH4+ and NO2−-N levels in shrimp culture reached above 1 ppm until the levels decreased to 0–0.5 ppm. The culture performance in the semi-mass trial at 500 PL/m3, 750 PL/m3, and 1,000 PL/m3 stocking densities was not significantly different for final mean body weight (12.06 ± 5.72, 11.84 ± 3.58, 12.04 ± 3.71 g/ind, respectively) and productivity (4.205 ± 0.071, 4.691 ± 0.025, 4.816 ± 0.129 kg/m3, respectively). Significant differences in survival (70 ± 7%, 53 ± 3%, 40 ± 4%, respectively) and feed conversion ratios (1.54 ± 0.01, 1.82 ± 0.00, 2.16 ± 0.03, respectively) were observed between the three different stocking densities. Water quality parameters and microbial loads during the semi-mass trial were similar for all stocking densities and were within the tolerance levels for white shrimp grow-out production. The results of the semi-mass trial showed that the hybrid ZWD-RAS system can maintain water quality and a microbial load up to a 1,000 PL/m3 stocking density; however, the optimum performance based on survival, feed conversion ratio, and productivity was reached at the 500 PL/m3 stocking density. The industrial trial of the application of the hybrid ZWD-RAS system using the optimal stocking density of 500 PL/m3 resulted in a comparable shrimp survival of 78% with a total production of 298 kg shrimp biomass (equal to a productivity level of 2.7 kg/m3). The overall results of both the semi-mass and industrial trials showed that the application of a hybrid ZWD-RAS system allows optimal shrimp survival and growth at the stocking density of 500 PL/m3 and has high potential for application in commercial shrimp grow-out production at low salinity levels.

Cultivable rhizospheric and endophytic bacteria were isolated from cilembu sweet potato during the 5 mth period post planting to assess the diversity and dynamics of its bacterial community. The number of colony forming units of rhizospheric bacteria was significantly higher than for the endophytic bacteria. The diversity and genera richness of the bacteria associated with cilembu sweet potato in the early stages of growth were higher than in the last stages. The different cultivable bacteria were identified using 16S rRNA gene sequencing as: Alphaproteobacteria (Methylobacterium, Sphingomonas, Paracoccus), Gammaproteobacteria (Klebsiella, Enterobacter, Pseudomonas, Serratia), Bacteroidetes (Chryseobacterium, Sphingobacterium), Firmicutes (Exiguobacterium, Bacillus, Staphylococcus) and Actinobacteria (Streptomyces, Arthrobacter, Kocuria, Microbacterium, Micrococcus). The nitrogen content in the soil may significantly affect the change of bacterial diversity in the rhizosphere during the growth of cilembu sweet potato. All isolates were capable of producing plant growth-promoting traits, alone or in combination, such as indole acetic acid production, phosphate solubilization, ammonia production, nitrogen fixation, cellulolytic and amylolytic activity. Keywords: Cilembu sweet potato, Endophyte, Ipomoea batatas, Plant growth-promoting (PGP), Rhizosphere

Terasi or shrimp paste is an Indonesian traditional seasoning made from fermented small shrimp or krill. Different indigenous microorganism community exhibit different physiological function due to lack standard in its materials and processing. This study aimed to determine physiological profiles and microorganism community in Cirebon shrimp paste fermentation. BIOLOG TM EcoPlate was used to obtain microbial physiological function of the krill and 2-months old shrimp paste. Microorganisms were later isolated from EcoPlate substrate to determine its community structure. Average Well Color Development (AWCD) from krill was thirty times higher than shrimp paste. Interestingly, this study revealed a shift of carbon source utilization at day-28 of fermentation from amino acid and polymer to phenolic compound. In addition, AWCD index increased in accordance with increased of microorganism community complexity at day-28. Within 56 days of fermentation there was a slightly increase in water, fat, and carbohydrate content. In contrast, there was decrease in protein, ash content, and acidity level from neutral to acid, with salinity level resulted in between 16.26% to 21.42%. We conclude that there is a change of microorganism community within shrimp paste fermentation corresponding to metabolism activity which affects the product quality.

The Influence of Nitrate in Metal Biocorrosion caused by Sulfate Reducing Bacteria from Saguling Hydropower. The corrosion facilitated and accelerated by the activities of microorganism is called biocorrosion. Sulfate reducing bacteria (SRB) is known as the bacteria that cause biocorrosion in anaerobic condition by using sulfate as the final electron acceptor. Biocorrosion reduces equipment lifetime and increases maintenance cost in industry. In the cooling system in Saguling hydropower, corrosion was commonly caused by utilization of contaminated water due to anorganic and organic waste, especially sulfate. In this research, sulfate reducing bacteria was isolated from biofilms in the cooling system of Saguling Hydropower. Molecular analysis using PCR-DGGE method with dsrB gene (350 bp) as molecular markers showed that SRB consortium contained 12 bands and assumed as different species of SRB. SRB consortium was tested to determine its biocorrosion activity over metal material of ST37 (carbon steel) and SUS304 (stainless steel). The consortium then treated with 7 different nitrate concentrations to determine its effect against the sulfate reducing bacteria activity. SRB consortium caused higher corrosion to ST37 than SUS304L, with the corrosion rate of 0.07660 mm/year and 0.00265 mm/year, respectively. Concentration of 10 mM nitrate effectively inhibited corrosion rate on ST37 and caused the changes in sulfate reducing bacteria communities, indicated by the disappearance of 6 bands in DGGE profile

This study was conducted to evaluate the use of cyanobacteria Arthrospira platensis and cladoceran Daphnia magna biomass as complementary protein and lipid sources in diet supplementation for common carp (Cyprinus carpio L.) nursery. Three experimental diets containing A. platensis and D. magna meal at different concentrations were compared to the commercial (control) diet. Each experimental diet (ED) was set to contain D. magna and A. platensis meal at a specific combination: 2% and 5%, 2% and 7%, and 4% and 5% for ED1, ED2 and ED3, respectively. The protein and lipid content of the experimental diets ranged from 43.20% to 44.60% dry weight (DW) and 10.64% to 13.42% DW, respectively; while the protein and lipid content of the control diet were 43.00% DW and 6.72% DW, respectively. After 20 days of feeding period, ED3 group obtained the highest final body weight (BW) (58.18 ± 35.24 mg), total biomass (1936 ± 1625 mg), food conversion rate (1.34 ± 0.04), and specific growth rate (12.86 ± 0.03% BW day–1) among all treatment groups (P > 0.05); while ED1 group obtained the highest survival (75.5% ± 7.47%) among all treatment groups (P > 0.05). The total bacterial count and total pathogenic Aeromonas sp. in the culture water of the treatment groups (ranged from 2.00 to 2.65 × 105 CFU mL–1 and 3.50 to 4.12 × 103 CFU mL–1, respectively) were lower compared to the water of the control group fed (3.73 × 105 and 4.70 × 103 CFU mL–1, respectively). No significant differences in physicochemical water quality parameters were observed among treatments (P > 0.05). The current study suggests that the combination of A. platensis and D. magna biomass can be used as complementary protein and lipid sources in diet supplementation for common carp larvae and can result in a comparable fish growth, survival and feed utilization in common carp culture at the nursery phase.

Terasi is a traditional fermented shrimp paste used in Indonesian dish as condiments. Due to its affordability, the paste is widely consumed among the general population, and thus has a great impact in Indonesia. Currently, small-scale or home industry is common for terasi production, and natural fermentation process is the traditional method. Fermentation process is considered complete when desired aromatic odors are obtained. However, this makes the fermentation process subjective, because the decision is solely dependent on the producer. Additionally, natural fermentation poses a higher risk for contamination of microbial pathogens. As a result, the quality of the final product varies greatly from region to region. Therefore, it is necessary to improve the quality of terasi by means of controlled fermentation. Hence, the objective of the research is to optimize the controlled fermentation condition of terasi by determining the most optimal ratio of mixed starter culture. Optimal fermentation conditions were determined by analyzing the effect of the various starter inoculum on the inner microbial community, and results indicated that mixed culture of Staphylococcus saprophyticus, Bacillus subtilis, and Lactobacillus murinus with ratio of 2:1:2 was the most effective for suppressing the growth of unwanted microorganisms. The difference in the microbial composition also resulted to a change in the metabolite profile of terasi.

Dip-coating is a facile method for membrane modification. In this work, composite polypropylene-based membrane (PP) with improved anti-organic fouling is prepared by coating polysulfone (PSf)/PEG400/ZnO layer on PP hollow fiber membrane. Separation properties and organic fouling tendency of the composite membrane are investigated during the peat water filtration. Results show that PSf/PEG400/ZnO layer is successfully deposited on PP membrane evidenced by scanning electron microscopy and fourier-transform infrared spectroscopy analysis. ZnO particles increase membrane hydrophilicity shown by decreasing water contact angle from ∼97.7 to 77.1, which results in higher pure water permeability (from ∼16 to ∼46 L.m−2. h−1. bar−1). Higher hydrophilicity also reduces organic fouling tendency of the membrane during peat water treatment. The flux recovery ratio increases from 63 % to 66 % while relative flux reduction decreases from 53 % to 44 %. The composite PP membrane (M-ZnO-40 %) is able to remove ∼70 % humic substances from peat water. Results of this study show that the addition PSf/PEG400/ZnO layer can effectively improve membrane permeability, selectivity, and anti-organic fouling of PP hollow fiber membrane.

Culture conditions are very important to CO2 bio-fixation related with the CO2 removal efficiency through biological process by microalgae photosynthesis activities. The aim of the research was to study how high CO2 utilization efficiency could reach in mix culture that supplied high CO2 concentration (2%, 5%, and 7%) continuously from the bottom of photobioreactor. The mix microalgae culture containing of Chlorella sp, Scenedesmusobliquus and Ankistrodemus sp. were cultivated in photobioreactor with various environmental treatments i.e light intensities, light periodism and temperatures whereas the fixed CO2 gas flow rate of 8 L.min-1. The results showed that microalgae growth was best at light intensity of 4000 lux for 16/8 hours light/darkness cycling, 30°C and 5% CO2 supplied, indicated by the highest dried biomass (g.L-1), the highest Carbon content was g.d-1 and highest CO2 removal efficiency (%) that were 2.7, 11.9, 49, respectively. However the highest CO2 utilization efficiency for bio-fixation phenomenon was obtained from culture that supplied by 2% CO2 concentration, the value was almost 2 fold than 5% CO2 supplied and 4 fold than 7% CO2 concentration supplied, respectively. Biological fixation of CO2 are greatly affected by the characteristics of the microalgae strains and their tolerance to environmental conditions.

Microbial enhanced oil recovery (MEOR) is a biological based technology to enhance crude oil (CO) recovery at old oil wells by manipulating function or structure or both of the microbial environments existing in oil reservoirs. Even if many biosurfactant-producing microbes can be found in different environments, the ability of Geobacillus toebii R-32639 to enhance CO recovery needs to be verified. In this study, artificial cores (ACs) are used to simulate the application of MEOR by three scenarios of injecting nutrients, microbial culture and bioproducts. The use of Geobacillus toebii R-32639 as biosurfactant producer enables a lowering by 25.3% of interfacial tension and by 14.1% of CO viscosity and also enables the degrading of a 7.4–28.8% fraction of (C12–C34) hydrocarbons after 7 days of incubation. The injection of microbial culture into a laboratory-scale CO reservoir of the AC for the desirable purpose of enhanced oil recovery could feasibly achieve an average recovery factor of 14.27% but lower by 5.50% the AC porosity and by 91.0% the AC permeability; this is the best-case scenario of the microbial core flooding (MCF) experiments. The simulation of MEOR by using bacterial strains of Geobacillus toebii R-32639 provides valuable insight into the use of MCF experiments to obtain greater oil production from existing reservoirs.

Microbial enhanced oil recovery (MEOR) is a proven tertiary recovery technique. Biosurfactant is a microbial bioproduct that plays an important role in MEOR applications. This study aimed to test biosurfactant stability using a design experiment based on response surface methodology. First, isolation and screening for potential biosurfactant-producing bacteria from crude oil samples was performed, followed by their characterization. A biosurfactant core flooding experiment was also conducted to examine bacterial activity on MEOR. Thirty-one sequential isolates of bacteria were screened based on qualitative and semi-qualitative parameters. One selected biosurfactant-producing bacterium was identified as Bacillus licheniformis DS1 based on phylogenetic analysis of the 16S rRNA gene. This bacterium had the highest emulsification activity (Ei24 = 65.19%) in light crude oil and could reduce the interfacial tension between oil and water with an effective critical-micelle concentration of 157.5 mg/L. The biosurfactant was observed as a growth-associated metabolite type and the Fourier transform infrared spectrum revealed that the biosurfactant produced belonged to a group of lipopeptides. The biosurfactant has good stability in maintaining emulsification activity at pH 4–10, high temperatures up to 120 °C, and with an NaCl concentration up to 10% (w/v). Based on response surface methodology using the Box–Behnken experimental design, the optimum condition for the most stable biosurfactant is pH 12, a 40 °C temperature and 10% salinity, with an Ei24 value of 94.28%. Core flooding experiments with biosurfactant resulted in 5.4% additional oil recovery. Therefore, this biosurfactant shows a high potential application for MEOR.

Microbial influenced corrosion that associated with biofilm has been one of the major problem in industry. It causes damage to equipment and infrastructure because of rapid material deterioration and often resulting in pipeline failures. Pipeline failures can lead to large economic losses and environmental problems. Synthetic chemical biocides are commonly used to prevent corrosion but are not effective against preformed biofilm on pipes and toxic to the environment. A new antimicrobial is being developed by using biosurfactant produced by indigenous oil reservoir bacteria Bacillus sp. to prevent and eradicate biofilm. This study aims to determine minimum inhibitory concentration (MIC), minimum biofilm inhibitory concentration (MBIC), and minimum biofilm eradication concentration for 50% eradication (MBEC50) of biosurfactant against biofilm forming bacteria isolated from oil resevoir, its effect on biofilm community structure and its ability to inhibit the corrosion rate of Carbon Steel ST37. MIC, MBIC, and MBEC50 were determined using broth macrodillution technique, biofilm community structure were analyzed using total plate count method, and corrosion rate of steel were determined using weight loss method. Biofilm and corroded steel surface was also visualized using SEM-EDS. From this study, it is revealed that MIC, MBIC, and MBEC50 values respectively are 62.5; 31.25; and 500 μg ml−1. Biosufactant is able to inhibit Pseudomonas sp. 1 and Pseudomonas sp. 2 attachment to Carbon Steel ST37 surface and also able to eradicate preformed biofilm on steel surface. This study also showed the reduction of corrosion rate in Carbon Steel ST 37 as a result of biosurfactants treatment; from 4.56 × 10−4 mm year−1 to 3.31 × 10−4 mm year−1 based on MBIC value and from 5.18 × 10−5 mm year −1 to 2.7 × 10−5 mm year−1 after biofilm eradication at MBEC value. The results showed that biosurfactant in this study could be a good candidate for a new anti-corrosion agent.