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Heterotrophic cultivation of microalgae for production of biodiesel

Mohamed MS, Wei LZ, Ariff AB

Recent Pat Biotechnol, 2011 Aug;5(2):95-107.
PMID: 21707527

High cell density cultivation of microalgae via heterotrophic growth mechanism could effectively address the issues of low productivity and operational constraints presently affecting the solar driven biodiesel production. This paper reviews the progress made so far in the development of commercial-scale heterotrophic microalgae cultivation processes. The review also discusses on patentable concepts and innovations disclosed in the past four years with regards to new approaches to microalgal cultivation technique, improvisation on the process flow designs to economically produced biodiesel and genetic manipulation to confer desirable traits leading to much valued high lipid-bearing microalgae strains.

Matched MeSH terms: Heterotrophic Processes/physiology
An improved enzyme assay for molybdenum-reducing activity in bacteria

Shukor MY, Rahman MF, Shamaan NA, Lee CH, Karim MI, Syed MA

Appl Biochem Biotechnol, 2008 Mar;144(3):293-300.
PMID: 18556818

Molybdenum-reducing activity in the heterotrophic bacteria is a phenomenon that has been reported for more than 100 years. In the presence of molybdenum in the growth media, bacterial colonies turn to blue. The enzyme(s) responsible for the reduction of molybdenum to molybdenum blue in these bacteria has never been purified. In our quest to purify the molybdenum-reducing enzyme, we have devised a better substrate for the enzyme activity using laboratory-prepared phosphomolybdate instead of the commercial 12-phosphomolybdate we developed previously. Using laboratory-prepared phosphomolybdate, the highest activity is given by 10:4-phosphomolybdate. The apparent Michaelis constant, Km for the laboratory-prepared 10:4-phosphomolybdate is 2.56 +/- 0.25 mM (arbitrary concentration), whereas the apparent V(max) is 99.4 +/- 2.85 nmol Mo-blue min(-1) mg(-1) protein. The apparent Michaelis constant or Km for NADH as the electron donor is 1.38 +/- 0.09 mM, whereas the apparent V(max) is 102.6 +/- 1.73 nmol Mo-blue min(-1) mg(-l) protein. The apparent Km and V(max) for another electron donor, NADPH, is 1.43 +/- 0.10 mM and 57.16 +/- 1.01 nmol Mo-blue min(-1) mg(-1) protein, respectively, using the same batch of molybdenum-reducing enzyme. The apparent V(max) obtained for NADH and 10:4-phosphomolybdate is approximately 13 times better than 12-phoshomolybdate using the same batch of enzyme, and hence, the laboratory-prepared phosphomolybdate is a much better substrate than 12-phoshomolybdate. In addition, 10:4-phosphomolybdate can be routinely prepared from phosphate and molybdate, two common chemicals in the laboratory.

Matched MeSH terms: Heterotrophic Processes
Fulltext The effect of dental unit waterline flushing on the quality of water in dental teaching center in Malaysia

Sa’adiah Shahabudin, Rohayu Hami, Lim, Lee-Sim, Amalina Salleh

Journal of Biomedical and Clinical Sciences, 2018;3(1):72-74.
MyJurnal

The aim of this study to assess the efficiency of flushing
method of Dental Unit Waterline (DUWL) system in reducing the
number of microorganism. Water samples were taken before and after
two minutes of flushing from air-water syringes system in ten randomly
selected dental units in a Dental Teaching Centre. These samples
were immediately transferred to the microbiology laboratory in the cool
box within 8 hours for the heterotrophic plate count (HPC) test. Paired
t-test was used to analyse number of microbe before and after flushing.
The numbers of colony forming unit (CFU) ranged from 13,000 to
120,000CFU/ml in unflushed samples, and 3,000 to 15,000CFU/ml in
flushed samples. The mean HPC post-flushing was lower than preflushing [8360.00 (4561.48) vs 63300.00 (44587.12) CFU/ml]. The
mean HPC between pre- and post-flushing was significantly different
(P=0.004, 95% CI 22039.52, 87840.48). The coliform count from the
control was 140 CFU/ml. In conclusion, flushing method of DUWL
system significantly reduces the number of microorganisms in the
dental unit. However, the level of microorganisms still does not meet
the standard guideline by Environmental Protection Agency for safe
drinking water, which should be below 500 CFU/ml. In our opinion, the
duration of flushing should be increased and additional chemical
treatments of the dental units should be implemented to ensure the
safety of patients and dental personnel.

Matched MeSH terms: Heterotrophic Processes
Isolation of Potential Bacteria as Inoculum for Biofloc Formation in Pacific Whiteleg Shrimp, Litopenaeus vannamei Culture Ponds

Kasan NA, Ghazali NA, Ikhwanuddin M, Ibrahim Z

Pak J Biol Sci, 2017;20(6):306-313.
PMID: 29023055 DOI: 10.3923/pjbs.2017.306.313

BACKGROUND AND OBJECTIVE: A new green technology to reduce environmental damages while optimizing production of Pacific Whiteleg shrimp, Litopenaeus vannamei was developed known as "Biofloc technology". Microbial communities in biofloc aggregates are responsible in eliminating water exchange and producing microbial proteins that can be used as supplemented feed for L. vannamei. This study aimed to isolate and identify potential bioflocculant-producing bacteria to be used as inoculum for rapid formation of biofloc.
MATERIALS AND METHODS: For the purpose of this study, bacterial communities during 0, 30 and 70 days of culture (DOC) of L. vannamei grow-out ponds were isolated and identified through phenotypic and 16S rDNA sequences analysis. Phylogenetic relationships between isolated bacteria were then evaluated through phylogenetic tree analysis. One-way analysis of variance (ANOVA) was used to compare the differences of microbial communities at each DOC.
RESULTS: Out of 125 bacterial isolates, nine species of bacteria from biofloc were identified successfully. Those bacteria species were identified as Halomonas venusta, H. aquamarina, Vibrio parahaemolyticus, Bacillus infantis, B. cereus, B. safensis, Providencia vermicola, Nitratireductor aquimarinus and Pseudoalteromonas sp., respectively. Through phylogenetic analysis, these isolates belong to Proteobacteria and Firmicutes families under the genera of Halomonas sp., Vibrio sp., Bacillus sp., Providencia sp., Nitratireductor sp. and Pseudoalteromonas sp.
CONCLUSION: In this study, bioflocculant-producing bacteria were successfully identified which are perfect candidates in forming biofloc to reduce water pollution towards a sustainable aquaculture industry. Presence of Halomonas sp. and Bacillus sp. in all stages of biofloc formation reinforces the need for new development regarding the ability of these species to be used as inoculum in forming biofloc rapidly.

Matched MeSH terms: Heterotrophic Processes
Fulltext Temporal variation of bacterial respiration and growth efficiency in tropical coastal waters

Lee CW, Bong CW, Hii YS

Appl Environ Microbiol, 2009 Dec;75(24):7594-601.
PMID: 19820145 DOI: 10.1128/AEM.01227-09

We investigated the temporal variation of bacterial production, respiration, and growth efficiency in the tropical coastal waters of Peninsular Malaysia. We selected five stations including two estuaries and three coastal water stations. The temperature was relatively stable (averaging around 29.5 degrees C), whereas salinity was more variable in the estuaries. We also measured dissolved organic carbon and nitrogen (DOC and DON, respectively) concentrations. DOC generally ranged from 100 to 900 microM, whereas DON ranged from 0 to 32 microM. Bacterial respiration ranged from 0.5 to 3.2 microM O2 h(-1), whereas bacterial production ranged from 0.05 to 0.51 microM C h(-1). Bacterial growth efficiency was calculated as bacterial production/(bacterial production + respiration), and ranged from 0.02 to 0.40. Multiple correlation analyses revealed that bacterial production was dependent upon primary production (r2 = 0.169, df = 31, and P < 0.02) whereas bacterial respiration was dependent upon both substrate quality (i.e., DOC/DON ratio) (r2 = 0.137, df = 32, and P = 0.03) and temperature (r2 = 0.113, df = 36, and P = 0.04). Substrate quality was the most important factor (r2 = 0.119, df = 33, and P = 0.04) for the regulation of bacterial growth efficiency. Using bacterial growth efficiency values, the average bacterial carbon demand calculated was from 5.30 to 11.28 microM C h(-1). When the bacterial carbon demand was compared with primary productivity, we found that net heterotrophy was established at only two stations. The ratio of bacterial carbon demand to net primary production correlated significantly with bacterial growth efficiency (r2 = 0.341, df = 35, and P < 0.001). From nonlinear regression analysis, we found that net heterotrophy was established when bacterial growth efficiency was <0.08. Our study showed the extent of net heterotrophy in these waters and illustrated the importance of heterotrophic microbial processes in coastal aquatic food webs.

Matched MeSH terms: Heterotrophic Processes