Response surface analysis for enzymatic decolorization of Congo red by manganese peroxidase

The enzymatic decolorization process of manganese peroxidase (MnP) is a complex system, which is greatly affected by the concentrations of H₂O₂, Mn²⁺, dye and enzyme. This work aimed to study these factors and investigate the combined interactions between them by applying response surface methodology (RSM) for decolorization of Congo red with MnP from Schizophyllum sp. F17, meanwhile conventional one-factor-at-a-time analysis was carried out. Through the one-factor-at-a-time analysis the optimized H₂O₂, Mn²⁺, Congo red and MnP extract was 0.2 mM, 0.5 mM, 50 mg/l and 0.8 ml, respectively, and the maximum decolorization attained under such conditions was 24.2%. Response surface analysis was conducted through Box–Behnken design and a second-order polynomial model (R² = 0.8565) was generated to describe the combined effect and the interactions quantificationally. ANOVA analysis indicated that the interactions between H₂O₂ and MnP, between dye and MnP were significant; the optimum condition through RSM was found to be 0.35 mM H₂O₂, 0.5 mM Mn²⁺, 75 mg/l Congo red and 1.4 ml MnP extract, for maximum decolorization of 30.8%.     

Optimizing l-(+)-lactic acid production by thermophile Lactobacillus plantarum As.1.3 using alternative nitrogen sources with response surface method

The effects of five alternative nitrogen sources, namely, malt sprout (MS), corn steep liquor (CSL), NH₄Cl, NH₄NO₃ and diamine citrate (DC) were investigated on the l-(+)-lactic acid (LA) production by thermophile Lactobacillus plantarum As.1.3. Through the statistical analysis of the results by three steps of response surface methodology (RSM) design, MS and CSL were found to have significant effects on the LA production and their optimal concentrations in the medium should be 16.0 g/L and 12.0 g/L, respectively. The verification of the optimized medium showed that the maximum specific growth rate (μ_m) was 1.09 h⁻¹, the cell yield coefficient (Y_X/S) and the l-(+)-lactic acid yield coefficient (Y_P/S) were 0.233 (OD₆₂₀/g) and 0.98 (g/g), and the maximum volumetric productivity and the average volumetric productivity were 13.0 g/L h and 3.20 g/L h, respectively. The results indicate that the LA production can also be enhanced with the inexpensive nitrogen source alternatives.     

Statistical media optimization for growth and PHB production from methanol by a methylotrophic bacterium

Media components were optimized by statistical design for cell growth and PHB production of Methylobacterium extorquens DSMZ 1340. Four important components of growth media were optimized by central composite design. The growth increased from an OD = 1.35 for Choi medium as control to an OD = 2.15 for optimal medium. Then media components for PHB production were optimized. Optimization of five important factors was conducted by response surface method. The optimal composition of PHB production medium was found to be at 7.8 (g/L) Na₂HPO₄ · 12H₂O, and surprisingly at zero concentration of (NH₄)₂SO₄, KH₂PO₄, MgSO₄ and MnSO₄. The PHB production was found to be 2.95 (g/L) at this medium. RSM results indicated that a deficiency of nitrogen and magnesium is crucial for PHB accumulation in this microorganism. Also, PHB production was carried out in a 5 L fermentor at the optimum condition which resulted in 9.5 g/L PHB and 15.4 g/L cell dry weight with 62.3% polymer content.     

Biotransformation of 2-phenylethanol to phenylacetaldehyde in a two-phase fed-batch system

Phenylacetaldehyde (PA) can be produced by the oxidation of 2-phenylethanol (PE) through biotransformation. In order to prevent substrate and product inhibitions and the transformation of the PA to phenylacetic acid (PAA), utilization of a two-phase system is very attractive. Gluconobacter oxydans B-72 was used as the microorganism and iso-octane as the solvent. The effect of initial substrate concentration on the PA production was investigated in single- and two-phase systems. In the single-phase system, substrate inhibition occurred above 5 g/l, and in the two-phase system, above 7.5 g/l. Substrate inhibition kinetics were also studied in the two-phase system and kinetic constants were determined as r_max=0.64 g/l min, K_M=8.15 g/l, K_PA=2.5 g/l. Because it was observed that two-phase system is insufficient to remove the substrate inhibition effect, fed-batch operation was utilised in this study. For 7.5 g/l of PE, 1.65, 3.85, and 7.35 g/l of PA were obtained in the single-phase, two-phase, and two-phase three fed-batch systems, respectively. Effect of biotransformation time, initial substrate concentration, agitation speed, and fed-batch number on the PA production was investigated in a two-phase fed-batch system by the response surface methodology (RSM). The optimum values were found as 3 fed-batch number, 2.75 g/l initial substrate concentration, 150 rpm agitation speed, and 65 min of one batch biotransformation time. In order to verify these results, an experiment was performed at these optimum conditions and 7.10 g/l of PA concentration was obtained.     

Effects of mulberry leaves to replace rapeseed meal on performance of sheep feeding on ammoniated rice straw diet

This study was conducted to investigate effects of leaves of mulberry tree (Morus alba) as a protein supplement to isonitrogenously replace rapeseed meal (RSM) on performance of growing lambs offered ammoniated rice straw (ABRS) (Trial 1), and to evaluate the digestive characteristics of the ABRS supplemented with different ratios of RSM and mulberry leaves in terms of in vitro gas production (Trial 2). In Trial 1, 45 Huzhou lambs were divided into five equal groups according to their body weight and gender. Lambs in each group were kept in three pens (male, female and mixed (one male and two females)), and received one of the following dietary treatments: 100 g RSM (A), 75 g RSM plus 60 g mulberry leaves (B), 50 g RSM plus 120 g mulberry leaves (C), 25 g RSM plus 180 g mulberry leaves (D), and 240 g mulberry leaves (E). All animals were given ABRS ad libitum along with 100 g ground corn per head per day. The intake of ABRS was slightly increased with the supplementary level of mulberry leaves, and hence total intake increased with the increasing level of mulberry leaves. The growth rates were higher in diets A and E than those in other treatments (P<0.05), with little difference between diets A and E, and the slowest in C. Animals of all genders showed a similar trend, though male lambs was higher in weight gain than the female. While feed efficiency was higher in diet A, concentrate consumption per kilogram of weight gain was lower when higher level of mulberry leaves was supplemented (diets D and E). Feed cost per kilogram gain was lower in diets E and A compared to other treatments. Degradation of dry matter in the rumen of sheep were higher for mulberry leaves than for RSM, but crude protein was less degraded for mulberry leaves than for RSM. The potential GP was significantly higher in diet A than those in B, C and D (P<0.05), and higher in E than in C (P<0.05) (Trial 2), indicating a negative associate effect of mulberry leaves and RSM on digestion. It is inferred that mulberry leaves may be used as a protein supplement to ammoniated straw diets to fully substitute for RSM, but these two supplements should unlikely be supplemented together to avoid the negative associate effect.     

Agrobacterium rosae sp. nov., isolated from galls on different agricultural crops

The plant tumorigenic strain NCPPB 1650^T isolated from Rosa × hybrida, and four nonpathogenic strains isolated from tumors on grapevine (strain 384), raspberry (strain 839) and blueberry (strains B20.3 and B25.3) were characterized by using polyphasic taxonomic methods. Based on 16S rRNA gene phylogeny, strains were clustered within the genus Agrobacterium. Furthermore, multilocus sequence analysis (MLSA) based on the partial sequences of atpD, recA and rpoB housekeeping genes indicated that five strains studied form a novel Agrobacterium species. Their closest relatives were Agrobacterium sp. R89-1, Agrobacterium rubi and Agrobacterium skierniewicense. Authenticity of the novel species was confirmed by average nucleotide identity (ANI) and in silico DNA–DNA hybridization (DDH) comparisons between strains NCPPB 1650^T and B20.3, and their closest relatives, since obtained values were considerably below the proposed thresholds for the species delineation. Whole-genome-based phylogeny further supported distinctiveness of the novel species, that forms together with A. rubi, A. skierniewicense and Agrobacterium sp. R89-1 a well-delineated sub-clade of Agrobacterium spp. named “rubi”. As for other species of the genus Agrobacterium, the major fatty acid of the strains studied was 18:1 w7c (73.42–78.12%). The five strains studied were phenotypically distinguishable from other species of the genus Agrobacterium. Overall, polyphasic characterization showed that the five strains studied represent a novel species of the genus Agrobacterium, for which the name Agrobacterium rosae sp. nov. is proposed. The type strain of A. rosae is NCPPB 1650^T (=DSM 30203^T = LMG 230^T = CFBP 4470^T = IAM 13558^T = JCM 20915^T).     

Description of Massilia rubra sp. nov., Massilia aquatica sp. nov., Massilia mucilaginosa sp. nov., Massilia frigida sp. nov., and one Massilia genomospecies isolated from Antarctic streams,lakes and regoliths

Bacteria of the genus Massilia often colonize extreme ecosystems, however, a detailed study of the massilias from the Antarctic environment has not yet been performed. Here, sixty-four Gram-stain-negative, aerobic, motile rods isolated from different environmental samples on James Ross Island (Antarctica) were subjected to a polyphasic taxonomic study. The psychrophilic isolates exhibited slowly growing, moderately slimy colonies revealing bold pink-red pigmentation on R2A agar. The set of strains exhibited the highest 16S rRNA gene sequence similarities (99.5–99.9%) to Massilia violaceinigra B2^T and Massilia atriviolacea SOD^T and formed several phylogenetic groups based on the analysis of gyrB and lepA genes. Phenotypic characteristics allowed four of them to be distinguished from each other and from their closest relatives. Compared to the nearest phylogenetic neighbours the set of six genome-sequenced representatives exhibited considerable phylogenetic distance at the whole-genome level. Bioinformatic analysis of the genomic sequences revealed a high number of putative genes involved in oxidative stress response, heavy-metal resistance, bacteriocin production, the presence of putative genes involved in nitrogen metabolism and auxin biosynthesis. The identification of putative genes encoding aromatic dioxygenases suggests the biotechnology potential of the strains. Based on these results four novel species and one genomospecies of the genus Massilia are described and named Massilia rubra sp. nov. (P3094^T = CCM 8692^T = LMG 31213^T), Massilia aquatica sp. nov. (P3165^T = CCM 8693^T = LMG 31211^T), Massilia mucilaginosa sp. nov. (P5902^T = CCM 8733^T = LMG 31210^T), and Massilia frigida sp. nov. (P5534^T = CCM 8695^T = LMG 31212^T).     

Flavobacterium circumlabens sp. nov. and Flavobacterium cupreum sp. nov., two psychrotrophic species isolated from Antarctic environmental samples

A taxonomic study of 24 Gram-stain-negative rod-shaped bacteria originating from the Antarctic environment is described. Phylogenetic analysis using 16S rRNA gene sequencing differentiated isolated strains into two groups belonging to the genus Flavobacterium. Group I (n = 20) was closest to Flavobacterium aquidurense WB 1.1-56^T (98.3% 16S rRNA gene sequence similarity) while group II (n = 4) showed Flavobacterium hydatis DSM 2063^T as its nearest neighbour (98.5–98.9% 16S rRNA gene sequence similarity). Despite high 16S rRNA gene sequence similarity, these two groups represented two distinct novel species as shown by phenotypic traits and low genomic relatedness assessed by rep-PCR fingerprinting, DNA-DNA hybridization and whole-genome sequencing. Common to representative strains of both groups were the presence of major menaquinone MK-6 and sym-homospermidine as the major polyamine. Common major fatty acids were C_15:0 iso, C_15:1 iso G, C_15:0 iso 3-OH, C_17:0 iso 3OH and Summed Feature 3 (C_16:1 ω7c/C_16:1 ω6c). Strain CCM 8828^T (group I) contained phosphatidylethanolamine, three unidentified lipids lacking a functional group, three unidentified aminolipids and single unidentified glycolipid in the polar lipid profile. Strain CCM 8825^T (group II) contained phosphatidylethanolamine, eight unidentified lipids lacking a functional group, three unidentified aminolipids and two unidentified glycolipids in the polar lipid profile. These characteristics corresponded to characteristics of the genus Flavobacterium. The obtained results showed that the analysed strains represent novel species of the genus Flavobacterium, for which the names Flavobacterium circumlabens sp. nov. (type strain CCM 8828^T = P5626^T = LMG 30617^T) and Flavobacterium cupreum sp. nov. (type strain CCM 8825^T = P2683^T = LMG 30614^T) are proposed.     

Rahnella victoriana sp. nov., Rahnella bruchi sp. nov., Rahnella woolbedingensis sp. nov., classification of Rahnella genomospecies 2 and 3 as Rahnella variigena sp. nov. and Rahnella inusitata sp. nov., respectively and emended description of the genus Rahnella

Isolations from oak symptomatic of Acute Oak Decline, alder and walnut log tissue, and buprestid beetles in 2009–2012 yielded 32 Gram-negative bacterial strains showing highest gyrB sequence similarity to Rahnella aquatilis and Ewingella americana. Multilocus sequence analysis (using partial gyrB, rpoB, infB and atpD gene sequences) delineated the strains into six MLSA groups. Two MLSA groups contained reference strains of Rahnella genomospecies 2 and 3, three groups clustered within the Rahnella clade with no known type or reference strains and the last group contained the type strain of E. americana. DNA–DNA relatedness assays using both the microplate and fluorometric methods, confirmed that each of the five Rahnella MLSA groups formed separate taxa. Rahnella genomospecies 2 and 3 were previously not formally described due to a lack of distinguishing phenotypic characteristics. In the present study, all five Rahnella MLSA groups were phenotypically differentiated from each other and from R. aquatilis. Therefore we propose to classify the strains from symptomatic oak, alder and walnut and buprestid beetles as: Rahnella victoriana sp. nov. (type strain FRB 225^T = LMG 27717^T = DSM 27397^T), Rahnella variigena sp. nov. (previously Rahnella genomosp. 2, type strain CIP 105588^T = LMG 27711^T), Rahnella inusitata sp. nov. (previously Rahnella genomosp. 3, type strain DSM 30078^T = LMG 2640^T), Rahnella bruchi sp. nov. (type strain FRB 226^T = LMG 27718^T = DSM 27398^T) and Rahnella woolbedingensis sp. nov. (type strain FRB 227^T = LMG 27719^T = DSM 27399^T).     

Production and statistical optimization of a novel olivanic acid by Streptomyces olivaceus MTCC 6820

A microbial strain, isolated from soil samples, characterized as Streptomyces olivaceus MTCC 6820 showed broad-spectrum antibacterial activity. The compound produced was chemically characterized as a new form of olivanic acid. Olivanic acid production was optimized statistically by Plackett-Burman design (PBD) and response surface methodology (RSM). Effects of soybean meal, glycerol, CaCO₃ and dl-alanine were investigated with the help of PBD. The individual and interaction effects of the studied variables were evaluated by RSM using central composite design (CCD). By applying statistical design, antibiotic production was enhanced nearly 8 times (415 mg/l) as compared with the normal production medium (50 mg/l).     

Inulinase overproduction by a mutant of the marine yeast Pichia guilliermondii using surface response methodology and inulin hydrolysis

In this study, in order to isolate inulinase overproducers from the marine yeast Pichia guilliermondii, its cells were treated by using UV light and LiCl. The mutant M-30 with enhanced inulinase production was obtained and was found to be stable after cultivation for 20 generations. Response surface methodology (RSM) was used to optimize the medium compositions and cultivation conditions for inulinase production by the mutant M-30 in liquid fermentation. Inulin, yeast extract, NaCl, temperature, pH for maximum inulinase production by the mutant M-30 were found to be 20.0 g/l, 5.0 g/l, 20.0 g/l, 28 °C and 6.5, respectively. Under the optimized conditions, 127.7 U/ml of inulinase activity was reached in the liquid culture of the mutant M-30 whereas the predicted maximum inulinase activity of 129.8 U/ml was derived from RSM regression. Under the same conditions, its parent strain only produced 48.1 U/ml of inulinase activity. This is the highest inulinase activity produced by the yeast strains reported so far. We also found that inulin could be actively converted into monosaccharides by the crude inulinase.     

Enhancing production of prodigiosin from Serratia marcescens C3 by statistical experimental design and porous carrier addition strategy

Serratia marcescens C3 produces a natural red-pigment, prodigiosin, which exhibits immunosuppressive properties, in vitro apoptotic effects, and in vivo anti-tumor activities. This work seeks to improve the production of prodigiosin by S. marcescens C3 using various strategies. Starch and peptone were identified as the optimized carbon and nitrogen sources for the production of prodigiosin, yielding a prodigiosin concentration of 2.3 g/L. This value was significantly increased to 6.7 g/L using a carbon/nitrogen ratio of 6/4 (starch/peptone = 16 g/L/10.67 g/L). To enhance prodigiosin production even further, a statistical experimental design methodology was utilized to optimize the composition of the culture medium that is utilized in the production of prodigiosin. Prodigiosin production of 7.07 g/L was achieved when the concentrations of two trace compounds, FeSO₄·4H₂O and MnSO₄·4H₂O, were optimized using the statistical experimental design methodology. Their optimal concentrations were 0.56 mM and 3.25 mM, respectively. Ultimately, the production of prodigiosin was increased from 2.3 g/L to 15.6 g/L, or by a factor of nearly seven by immobilizing microorganisms in 3% calcium alginate beads.     

Neuromuscular fatigue during a prolonged intermittent exercise: Application to tennis

The time course of alteration in neuromuscular function of the knee extensor muscles was characterized during a prolonged intermittent exercise. Maximal voluntary contraction (MVC) and surface EMG activity of both vastii were measured during brief interruptions before (T₀), during (30, 60, 90, 120, 150 and 180 min: T₃₀, T₆₀, T₉₀, T₁₂₀, T₁₅₀, T₁₈₀) and 30 min after (T₊₃₀) a 3 h tennis match in 12 trained players. M-wave and twitch contractile properties were analyzed following single stimuli. Short tetani at 20 Hz and 80 Hz were also applied to six subjects at T₀ and T₁₈₀. Significant reductions in MVC (P < 0.05; −9%) and electromyographic activity normalized to the M wave for both vastii (P < 0.01) occurred with fatigue at T₁₈₀. No significant changes in M-wave duration and amplitude nor in twitch contractile properties were observed. The ratio between the torques evoked by 20 Hz and 80 Hz stimulation declined significantly (P < 0.001; −12%) after exercise. Central activation failure and alterations in excitation–contraction coupling are probable mechanisms contributing to the moderate impairment of the neuromuscular function during prolonged tennis playing.     

The effect of time left alone at home on dog welfare

The aim of this study was to investigate the effect of time left alone on dog behaviour and cardiac activity. Twelve privately owned dogs, with no history of separation related behaviour problems, were video-recorded on three different occasions when left alone in their home environment. The treatments lasted for 0.5 h (T_0.5); 2 h (T₂) and 4 h (T₄). Video-recording started 10 min before the owner left the house and continued until 10 min after the owner returned, so that interactions between dog and owner as well as behaviour during separation could be studied. Data on heart rate (HR) and heart rate variability (HRV) were collected within the same time period in each treatment. In addition to analysing behaviours separately, behaviours were also grouped together and defined as new variables; physically active, attentive behaviour, vocal, interaction initiated by owner and interaction initiated by dog. There were no differences in behaviour between treatments at equivalent time intervals until the owner returned, although a number of differences were observed at reunion with the owner. Dogs showed a higher frequency of physical activity (P < 0.05) and attentive behaviour (P < 0.01) in T₂ (0.37 ± 0.07; 0.52 ± 0.08, mean frequency of occurrence/15 s ± SE) and T₄ (0.48 ± 0.08; 0.48 ± 0.07) compared to T_0.5 (0.20 ± 0.07; 0.21 ± 0.05). They also showed more tail wagging (P < 0.01) and interacted more with their owners (P < 0.01) in T₂ (0.27 ± 0.08; 0.47 ± 0.09) and T₄ (0.26 ± 0.04; 0.42 ± 0.09) compared to T_0.5 (0.09 ± 0.04; 0.14 ± 0.03). After a longer time of separation, the dogs also showed higher frequencies of lip licking (P < 0.05) and body shaking (P < 0.05) at the owner's return (T_0.5 = 0.09 ± 0.05; T₂ = 0.24 ± 0.08; T₄ = 0.27 ± 0.06 and T_0.5 = 0.03 ± 0.01; T₂ = 0.08 ± 0.03; T₄ = 0.07 ± 0.01, respectively). There was a tendency for higher HR (P < 0.1) during the first and second minute after reunion in T₂ (127.6 ± 1.25, mean bpm ± SE; 111.3 ± 1.24) compared to T_0.5 (106.2 ± 1.06; 87.5 ± 1.02). According to the results of this study, the effect of time left alone was shown by a more intense greeting behaviour by the dog towards their owner as well as by a higher frequency of physical activity and attentive behaviour when the owner returned, already after 2 h of separation. Although this study cannot distinguish between whether dogs were aware of the length of time they were alone (but did not signal it) or whether they were unaware until reminded of it by the return of their owner, it does confirm that dogs are affected by the duration of time at home alone.     

Characterization of the extracellular biodemulsifier of Bacillus mojavensis XH1 and the enhancement of demulsifying efficiency by optimization of the production medium composition

The demulsifying bacterium XH1 was identified as a Bacillus mojavensis by the 16S rDNA gene. The extracellular biodemulsifier produced by this species was purified by ethanol extraction and column chromatography through a sephadex and silicon gel column. Preliminary investigation using UV–vis and TLC indicated that the biodemulsifier had two components a protein and a lipopeptide. All major components of the medium, including the sources of soluble and insoluble carbon, nitrogen, phosphate, and metal ions were investigated to improve the biosynthesis and efficiency of the biodemulsifier. The optimal carbon sources were glucose and liquid paraffin. Glucose participated in the biosynthesis of the demulsifier, while liquid paraffin promoted the lipophilicity and secretion of biosurfactants. The absence of yeast extract, ammonium chloride or phosphate (K₂HPO₄/KH₂PO₄) had a negative effect on the production of the biodemulsifier and significantly inhibited its activity. To further enhance the biodemulsifier efficiency, the optimal medium composition was determined using the response surface methodology (RSM) based on the central composite rotation design (CCRD). Using the optimized biodemulsifier production medium: 8.5 g/l glucose; 3% (v/v) liquid paraffin; 1.5 g/l yeast extract; 3.36 g/l NH₄Cl and15 g/l phosphate, the demulsifying ratio increased 35.5% and biodemulsifier yield increased to 2.07 g/l.     

Glutathione S-transferase pi (GST-pi) inhibition and anti-inflammation activity of the ethyl acetate extract of Streptomyces sp. strain MJM 8637

To investigate the anti-cancer properties of soil-borne actinobacteria, MJM 8637, the glutathione S-transferase pi (GST-pi) assay, anti-tumor necrosis factor (TNF)-α assay, the level of antioxidant potential by DPPH radical scavenging activity, NO scavenging activity, and ABTS radical scavenging activity in ethyl acetate extract were determined. The 16S rDNA sequencing analysis revealed that Streptomyces sp. strain MJM 8637, which was isolated from Hambak Mountain, Korea, has 99.5% similarity to Streptomyces atratus strain NBRC 3897. The physiological and the morphological characteristics of the strain MJM 8637 were also identified. The ethyl acetate extract of MJM 8637 inhibited TNF-α production approximately 61.8% at concentration 100 μg/ml. The IC₅₀ value of the strain MJM 8637 extract on GST-pi was identified to be 120.2 ± 1.6 μg/ml. In DPPH, NO, and ABTS radical scavenging assays, the IC₅₀ values of the strain MJM 8637 extract were found to be 977.2 μg/ml, 1143.7 μg/ml, and 454.4 μg/ml, respectively. The ethyl acetate extract of the strain MJM 8637 showed 97.2 ± 1.3% of cell viability at 100 μg/ml in RAW 264.7 cell viability assay. The results obtained from this study suggest that the ethyl acetate extract of Streptomyces sp. strain MJM 8637 could be considered as a potential source of drug for the cancers that have multidrug resistance with its GST-pi inhibition and anti-inflammation activities, and low cytotoxicity.     

Predation potential and biology of Protogamasellopsis posnaniensis Wisniewski & Hirschmann (Acari: Rhodacaridae)

Rhodacaridae are cosmopolitan mites mentioned as predators, although nothing is known about their potential as biological control agents. One of the objectives of the work reported in this paper was to evaluate the potential of Protogamasellopsis posnaniensis (Acari: Rhodacaridae) as predator of representative species of insects of the families Sciaridae (Bradysia matogrossensis (Lane)) and Thripidae (Frankliniella occidentalis (Pergande)), of mites of the family Acaridae (Tyrophagus putrescentiae (Schrank) and Rhizoglyphus echinopus (Fumouze & Robin) and of nematodes of the family Rhabditidae (Protorhabditis sp.). Another objective was to determine the biological cycle of P. posnaniensis when fed the prey on which it performed best in the preceding predation test. The study was conducted in a laboratory where the experimental units were maintained at 25 ± 1 °C, 97 ± 3% RH and in the dark. Although the predator was able to kill all prey species considered in this study, the most favorable prey were T. putrescentiae, F. occidentalis and Protorhabditis sp. Survivorship of the predator in predation tests was always 98% or higher. Life table biological parameters when the predator was fed T. putrescentiae were: R_o = 109.29; T = 19.06 days; λ = 1.28 e r_m = 0.32 female/female/day. Despite preying upon larvae of B. matogrossensis, eggs of the former can also be killed by the latter. The results indicated that P. posnaniensis is a promising biological control agent, deserving additional studies on its possible use for the control of soil pests.     

l-Lactic acid production from liquefied cassava starch by thermotolerant Rhizopus microsporus: Characterization and optimization

The thermotolerant Rhizopus microsporus DMKU 33 capable of producing l-lactic acid from liquefied cassava starch was isolated and characterized for its phylogenetic relationship and growth temperature and pH ranges. The concentrations of (NH₄)₂SO_4, KH₂PO₄, MgSO₄ and ZnSO₄·7H₂O in the fermentation medium was optimized for lactic acid production from liquefied cassava starch by Rhizopus microsporus DMKU 33 in shake-flasks at 40 °C. The fermentation was then studied in a stirred-tank bioreactor with aeration at 0.75 vvm and agitation at 200 rpm, achieving the highest lactic acid production of 84 g/L with a yield of 0.84 g/g at pH 5.5 in 3 days. Lactic acid production was further increased to 105–118 g/L with a yield of 0.93 g/g and productivity of 1.25 g/L/h in fed-batch fermentation. R. microsporus DMKU 33 is thus advantageous to use in simultaneous saccharification and fermentation for l-lactic acid production from low-cost starchy substrates.     

Application of polyethylene glycol immobilized Clostridium sp. LS2 for continuous hydrogen production from palm oil mill effluent in upflow anaerobic sludge blanket reactor

A novel polyethylene glycol (PEG) gel was fabricated and used as a carrier to immobilize Clostridium sp. LS2 for continuous hydrogen production in an upflow anaerobic sludge blanket (UASB) reactor. Palm oil mill effluent (POME) was used as the substrate carbon source. The optimal amount of PEG-immobilized cells for anaerobic hydrogen production was 12% (w/v) in the UASB reactor. The UASB reactor containing immobilized cells was operated at varying hydraulic retention times (HRT) that ranged from 24 to 6 h at 3.3 g chemical oxygen demand (COD)/L/h organic loading rate (OLR), or at OLRs that ranged from 1.6 to 6.6 at 12 h HRT. The best volumetric hydrogen production rate of 336 mL H₂/L/h (or 15.0 mmol/L/h) with a hydrogen yield of 0.35 L H₂/g COD_removed was obtained at a HRT of 12 h and an OLR of 5.0 g COD/L/h. The average hydrogen content of biogas and COD reduction were 52% and 62%, respectively. The major soluble metabolites during hydrogen fermentation were butyric acid followed by acetic acid. It is concluded that the PEG-immobilized cell system developed in this work has great potential for continuous hydrogen production from real wastewater (POME) using the UASB reactor.     

Kinetic modeling and implementation of superior process strategies for β-galactosidase production during submerged fermentation in a stirred tank bioreactor

This paper reports development and implementation of superior fermentation strategies for β-galactosidase production by Lactobacillus acidophilus in a stirred-tank bioreactor. Process parameters (aeration and agitation) were optimized for the process by application of Central Composite Design. Aeration rate of 0.5 vvm and agitation speed of 250 rpm were most suitable for β-galactosidase production (2001.2 U/L). Further improvement of the operation in pH controlled environment resulted in 2135 U/L of β-galactosidase with productivity of 142.39 U/L h. Kinetic modeling for biomass and enzyme production and substrate utilization were carried out at the aforementioned pH controlled conditions. The logistic regression model (X₀ = 0.01 g/L; X_max = 2.948 g/L; μ_max = 0.59/h; R² = 0.97) was used for mathematical interpretation of biomass production. Mercier's model proved to be better than Luedeking–Piret model in describing β-galactosidase production (P₀ = 0.7942 U/L; P_max = 2169.3 U/L; P_r = 0.696/h; R² = 0.99) whereas the latter was more efficient in mathematical illustration of lactose utilization (m = 0.187 g/g h; Y_x/s = 0.301 g/L; R² = 0.98) among the two used in this study. Strategies like fed-batch fermentation (3694.6 U/L) and semi-continuous fermentation (5551.9 U/L) further enhanced β-galactosidase production by 1.8 and 2.8 fold respectively.