Overproduction of a mosquitocidal chloramphenicol-resistant Lysinibacillus sphaericus mutant obtained through UV irradiation

A highly active mosquitocidal mutant UV-chloramphenicol-resistant mutant (UCR-146) of Lysinibacillus sphaericus 2362 was isolated by UV irradiation and selected through resistance to chloramphenicol which was inhibitory for growth of the parent strain. The growth of UCR-146 in NYSMCL at different concentrations of chloramphenicol (20–100 µg/ml) showed high mosquitocidal activity against Culex pipiens larvae with the optimum concentration of 35µg/ml. At this level, LC₅₀ of UCR-146 was decreased about five times from that of L. sphaericus 2362. Comparative efficiency of mosquitocidal activity of UCR-146 and L. sphaericus 2362 within 28 days of consecutive growth exhibited notable stability of both cultures through seven cycles of growth in their optimal media. UCR-146 was grown in industrial by-products media for production of the binary toxin under economic conditions. Offal medium at 2% showed the highest mosquitocidal activity of UCR-146 with LC₅₀ of 0.53 PPM which was 16.6, 13, 12.3 and 3.4 times less than that produced with L. sphaericus 2362 grown in NYSM, L. sphaericus 2362 grown in offal, UCR-146 grown in NYSM and UCR-146 grown in NYSMCL, respectively. Hence, the mosquitocidal activity of L. sphaericus 2362 increased several times through ultraviolet (UV) irradiation followed by chloramphenicol resistance selection and then growth in 2% offal medium. Finally, this procedure for selecting UV-chloramphenicol-resistant mutant and the medium used could potentially be a simple and cost effective approach for obtaining and producing a highly active mosquitocidal mutant.     

Dynamics of bacterial communities during solid-state fermentation using agro-industrial wastes to produce poly-γ-glutamic acid,revealed by real-time PCR and denaturing gradient gel electrophoresis (DGGE)

The dynamics of bacterial communities play an important role in solid-state fermentation (SSF). Poly-γ-glutamic acid (γ-PGA) was produced by Bacillus amyloliquefaciens C1 in SSF using dairy manure compost and monosodium glutamate production residuals as basic substrates. The production of γ-PGA reached a maximum of 0.6% after 20 days fermentation. Real-time polymerase chain reaction showed the amount of total bacteria reached 3.95 × 10⁹ 16S rDNA copies/g sample after 30 days, which was in good accordance with the 4.80 × 10⁹ CFU/g obtained by plate counting. Denaturing gradient gel electrophoresis profile showed a reduction of microbial diversity during fermentation, while the inoculum, B. amyloliquefaciens C1, was detected as the dominant organism through the whole process. In the mesophilic phase of SSF, Proteobacteria was the dominant microbial, which was replaced by Firmicutes and Actinobacteria in the thermophilic phase. The molecular analysis of the bacterial diversity has significant potential for instructing the maturing process of SSF to produce γ-PGA at a large-scale level, which could be a benefit in the production of high quality and stable SSF products.     

Survivability and storage stability of Trichoderma atroviride TRS40 preserved by fluidised bed drying on various agriculture by-products

Agriculture by-products were applied to proliferate biomass of Trichoderma atroviride TRS40 in solid state fermentation (SSF) cultures. The culture media overgrown with mycelium together with conidia were preserved by fluidised bed drying at various temperatures (50°C, 60°C and 70°C) and the received biopreparations were stored for 12 months. In order to determine the suitability of TRS40 in the production of biopreparations, the influence of preservation process and storage time on their survivability was examined. The three-component mixture proved more effective in the SSF cultures, ensuring TRS40 count at 6.07?×?10^9?CFU/g?dm, which was ca. 6 times higher than in the mono-component medium. TRS40 survivability after preservation at various temperatures ranged from 40.4% to 100%, regardless of carrier type. In turn, after 12-month storage of the biopreparations produced on the three-component medium, regardless of drying temperature, the number of viable cells ranged from 2.43?×?10⁸ to 2.49?×?10^8?CFU/g?dm. Furthermore, selected parameters of growth kinetics in the Bioscreen C system were determined. The storage time of biopreparations had various effects on growth kinetic parameters. In addition, the preserved preparations based on the TRS40 retained their capability for biosynthesis of hydrolases, even after 12 months of storage.     

Economic production of Lysinibacillus sphaericus under solid state fermentation

A highly active mosquitocidal Lysinibacillus sphaericus namely Ls 9B24 was isolated from soil of Alexandria governorate in Egypt. It was more active than the standard strain, L. sphaericus 2362. The sporulation and toxin formation of both cultures grown on different leguminous seeds and by-products under solid state fermentation (SSF) were studied. Among the tested substrates, 6% cotton seed meal enhanced sporulation and the mosquitocidal activity of L. sphaericus 2362, while 6% fodder yeast enhanced sporulation and the mosquitocidal activity of Ls 9B24. The optimum SSF growth conditions for maximum mosquitocidal activity by both cultures were using coarse wheat bran as a carrier material, 50% initial moisture content, 4–64 × 10⁶ colony forming units (CFU)/g solid medium inoculum and 6 days’ incubation period at 30°C. Addition of 0.5% yeast extract enhanced toxicity about 2.2 and 1.8 fold for L. sphaericus 2362 and Ls 9B24, respectively.     

金龟子绿僵菌在森林土壤中的分布及对松墨天牛致病性测定

松墨天牛是重大森林植物检疫性病害——松材线虫病的主要媒介昆虫。本研究于2005年8月～2006年8月从福建、江西两省共110个林分样区(其中松林88个样区)采集土壤样品330份,采用选择性培养基分离土壤中的金龟子绿僵菌。从21个样区的26份土样中分离出的金龟子绿僵菌占采集样区的19．1％和样品的7．9％,成菌落数(CFU)500～72500CFU/g,表明金龟子绿僵菌在森林土壤中有较为广泛的分布。对分离到的9个产孢量高的菌株,采用浸渍法(1×10~7孢子/mL)接种3～4龄健康松墨天牛幼虫,采用跗节接种法接种2～15日龄健康成虫,测定其致病力。结果表明,MaYTTR-03、MaYTTR-04菌株对松墨天牛幼虫和成虫均有较高致病力,表现出良好的生防潜力。     

Quantitative and qualitative study of the bacterial flora of farmed freshwater prawn (Macrobrachium rosenbergii) larvae

Quantitative and qualitative studies of the bacterial flora of farmed freshwater prawn (Macrobrachium rosenbergii) larvae in Saudi Arabia were performed, and isolates identified where possible. Physico‐chemical characteristics, bacterial counts, and the nature of the bacterial flora of larvae rearing tank water, sediment, tank wall surfaces, larval surface, supplied water, and feed were investigated. Bacterial counts ranged from 2.1 ± 1.3 × 10⁵ to 2.2 ± 0.8 × 10⁷ colony forming units (CFU) ml^?1 in tank water; 4.4 ± 0.9 × 10⁷ to 8.3 ± 1.7 ×10⁹ CFU g^?1 in tank sediment; 8.6 ± 1.0 × 10² to 9.8 ±0.7 × 10⁴ CFU cm^?2 on the tank wall surface; 1.3 ± 1.1 × 10⁴ to 7.7 ± 1.6 × 10⁶ CFU per larva surface, 7.9 ± 1.2 × 10⁵ to 5.0 ± 1.5 × 10⁷ CFU g^?1 in washed larval tissue slurries, 9.1 ± 0.7 × 10³ CFU ml^?1 in supplied water, and 2.4 ± 1.9 ×10¹⁰ CFU g^?1 in mixed feed. Fourteen bacterial genera were identified, including Chryseomonas sp., Vibrio spp., Cellulomonas sp., Aeromonas hydrophila, and Pasteurella sp. The tank water and sediment had similar bacteria to those on the prawn larvae. Chryseomonas sp., Cellulomonas sp. and Vibrio sp. were the most dominant species (prevalence >10%) in tank water; Chryseomonas sp., Pseudomonas alcaligenes and Shewanella putrefaciens in the sediment; Ps. alcaligenes and Cellulomonas sp. on the tank wall surface; Chryseomonas sp., and Cellulomonas sp. on the larval surface; and Chryseomonas sp., Vibrio vulnificus, Sh. putrefaciens and V. alginolyticus in the washed larval tissue slurries (prevalence 10%). Pseudomonas alcaligenes, Moraxella sp., Serratia liquefaciens, Gordona sp. and Burkholderia glumae were absent in larvae but identified in the culture water, tank sediment, and tank wall surface. Pseudomonas sp., Chryseomonas sp., Pasteurella sp. and V. alginolyticus were the prevalent bacteria (>12%) in supplied water. The feed contained V. alginolyticus, A. hydrophila and Cellulomonas sp. as the dominant bacteria (>13%). In the culture water and larvae samples, 83% of the feed and supplied water bacteria were identified.     

金龟子绿僵菌在森林土壤中的分布及对松墨天牛致病性测定

松墨天牛是重大森林植物检疫性病害——松材线虫病的主要媒介昆虫。本研究于2005年8月～2006年8月从福建、江西两省共110个林分样区（其中松林88个样区）采集土壤样品330份,采用选择性培养基分离土壤中的金龟子绿僵菌。从21个样区的26份土样中分离出的金龟子绿僵菌占采集样区的19.1%和样品的7.9%,成菌落数（CFU）500～72500CFU/g,表明金龟子绿僵菌在森林土壤中有较为广泛的分布。对分离到的9个产孢量高的菌株,采用浸渍法（1×10⁷孢子/mL）接种3～4龄健康松墨天牛幼虫,采用跗节接种法接种2～15日龄健康成虫,测定其致病力。结果表明,MaYTTR-03、MaYTTR-04菌株对松墨天牛幼虫和成虫均有较高致病力,表现出良好的生防潜力。     

Development of emulsion from rhizobial fermented starch industry wastewater for application as Medicago sativa seed coat

Starch industry wastewater was efficiently employed for the production of Sinorhizobium meliloti and the concentrated culture was used for the development of a biofertilizer formulation. Tween‐80 (0.02 g/L) acted as the best emulsifier for a Sinorhizobium–canola oil emulsion. The stability of the emulsion and survival of the organism was enhanced by supplementation of xanthan gum at pH 8. The refrigerated condition was most favorable for stability and survival of the microorganism. The survival of microorganism at 4±1°C was 2.78×10¹⁰ and 2.01×10¹⁰ CFU (colony forming unit)/mL on storage for 1 and 2 months, respectively. The values were higher than the prescribed cell count (×10³ CFU/mL) for field application. At 40°C, the survival of bacteria reduced from 3×10¹⁰ CFU/mL to 8.1×10⁹ and 8.8×10⁶ CFU/mL in 1 and 2 months, respectively. Emulsion‐coated seed was incubated at different temperatures and a cell count of 10⁵ CFU/seed was observed after 2 months of storage at 4°C, which was equal to the highest level of the described requirement (10³–10⁵ CFU/seed). Emulsion supplemented with xanthan gum improved the shelf‐life under optimized conditions (Sinorhizobium concentrate – canola oil (1:1) emulsion with 0.02 g/L Tween‐80; storage at pH 8 and temperature 4±1°C) and this emulsion with the required cell count and prolonged viability was used for the pre‐inoculation of seed or for in situ soil application.     

Dietary Mannan-oligosaccharides potentiate the beneficial effects of Bifidobacterium bifidum in broiler chicken

This study investigated the effects of dietary Bifidobacterium bifidum (BFD) and mannan-oligosaccharide (MOS), as a synbiotic, on the production performance, gut microbiology, serum biochemistry, antioxidant profile and health indices of broiler chicken. Six dietary treatments were T1 (negative control), T2 (positive control-20 mg antibiotic BMD kg⁻¹ diet; BMD: bacitracin methylene disalicylate), T3 (0·1% MOS + 10⁶ CFU BFD per g feed), T4 (0·1% MOS + 10⁷ CFU BFD per g feed), T5 (0·2% MOS + 10⁶ CFU BFD per g feed) and T6 (0·2% MOS + 10⁷ CFU BFD per g feed). Significantly (P < 0·01) better growth performance and efficiency was observed in birds supplemented with 0·2% MOS along with 10⁶ CFU BFD per g of feed compared to BMD and control birds. Supplementation with 0·2% MOS along with either 10⁶ or 10⁷ CFU BFD per g feed reduced (P < 0·01) the gut coliform, Escherichia coli, total plate count, and Clostridium perfringens count and increased the Lactobacillus and Bifidobacterium count. Significantly (P < 0·01) higher serum and liver antioxidant enzyme pool, serum HDL cholesterol and lower serum glucose, triglyceride, total cholesterol, cardiac risk ratio, atherogenic coefficient and atherogenic index of plasma were observed in birds supplemented with 0·2% MOS along with 10⁶ CFU BFD per g of feed compared to control or BMD supplemented birds. Better production performance, gut microbial composition, serum biochemistry, antioxidant profile and health indices were depicted by broiler chicken supplemented with 0·2% MOS and 10⁶ CFU BFD per g of feed.     

Microbial population,stability and maturity analysis of rotary drum composting of water hyacinth

Water hyacinth is a noxious aquatic weed growing over a wide variety of wetland. One of the effective methods of its treatment is rotary drum composting. Hence, microbial succession in the rotary drum composting of water hyacinth was studied along with stability and maturity. Different ratios of water hyacinth, cow dung and sawdust, i.e. 8: 1: 1, 7: 2: 1, 6: 3: 1, 5: 4: 1 and 10: 0: 0 (control), respectively, were taken. A total weight of 150 kg was maintained. Maximum degradation was observed in the trial 3 (6: 3: 1), which showed maximum temperature rise up to 56.5°C. The total mesophilic bacterial count changed from 4.73 × 10¹² to 2.5 × 10⁷ colony forming unit (CFU)/g compost during the composting period. Spore forming population reached the highest count of 3.3 × 10¹⁰ CFU/g in the thermophilic phase of composting. Actinomycetes, streptomycetes and fungi counts decreased to about 2.4 × 10⁷ CFU/g, 6.5×10⁵ CFU/g and 6.79 × 10⁵ CFU/g, respectively, at the end of composting period. A maximum reduction of 78.7% in oxygen uptake rate and 90.6% in CO₂ evolution rate was observed. This showed the highest stability of the compost sample. But the maximum volatile solids reduction of 45.9% signified the high content of recalcitrant lignocellulosic material. Indicator organisms were reduced to acceptable standards of sanitation.     

电解水的抑菌活性及对食品加工表面材料的消毒效果

为了考查应用电解水消除细菌污染的可行性,对氧化电解水的杀菌效果及对食品加工表面材料的消毒效果进行了研究。结果表明,含0.1%NaCl的自来水经7min的电解后所获得的氧化电解水,能在2min内将菌液浓度分别为4.20×106CFU/mL,2.18×106CFU/mL,1.44×106CFU/mL,2.10×106CFU/mL,1.94×106CFU/mL的埃希氏大肠杆菌(Escherichia coliO157:H7)、沙门氏菌(Salmonella enteritidis)、单核细胞增生李斯特菌(Listeria monocytogenes)、摩化摩根菌(Morganella morganii)、副溶血性弧菌(Vibrio parahaemolyticus)几乎全部杀死。另外,对食品加工表面接触材料中的地板砖、不锈钢板、瓷砖进行染菌消毒试验结果表明,含0.1%NaCl的电解水同样能将上述浓度的菌液感染到食品表面接触材料后在5min之内几乎全部将其杀死,是一种理想的食品表面材料消毒剂。     

A comparative study of Taxol production in liquid and solid‐state fermentation with Nigrospora sp. a fungus isolated from Taxus globosa

Aims: To determine in liquid (LF) and solid‐state fermentation (SSF) the effect of medium concentration on growth and Taxol produced by Nigrospora sp., a fungus isolated from the Mexican yew. Methods and Results: Nigrospora sp. was grown at different concentrations of the base culture medium M1D, i.e. two (2×), four (4×), six (6×) and eight times (8×) the base concentration. The titres of Taxol determined by competitive inhibition enzyme immunoassay increased with increasing medium concentration in LF and SSF but were higher in SSF in every medium concentration. The Taxol produced in SSF and LF with 8× medium was 221 and 142 ng l^?1. The SSF gave also higher biomass, growth and sugar utilization than LF in every medium. The growth and sugar consumption were modelled by the logistic and the Pirt models, respectively. However, the Luedeking–Piret model was unsuitable for Taxol. Conclusions: The SSF surpassed LF in terms of Taxol, growth and sugar utilization; thus, it has significant advantages over LF. Significance and Impact of the Study: This is the first report on Taxol production by SSF and the first contribution to evaluate the influence of the medium on Taxol production in LF and SSF.     

Pine processionary moth (Thaumetopoea pityocampa,Lepidoptera: Thaumetopoeidae) larvae are highly susceptible to the entomopathogenic fungi Metarhizium brunneum and Beauveria bassiana

The larvae of the pine processionary moth (PPM), Thaumetopoea pityocampa, feed on the needles of pine and cedar. The urticating hairs of older instars pose a threat to human and animal health. Strains of the entomopathogenic fungi, Metarhizium brunneum (V275, ARSEF 4556) and Beauveria bassiana (KTU-24), were assayed against first to fourth instar T. pityocampa using doses ranging from 1?×?10⁵ to 1?×?10⁸ conidia mL^?1. The three strains differed slightly in their virulence but caused 100% mortality of all instars at the highest dose. The newly emerged or first instar larvae were extremely susceptible with 100% mortality being achieved 2–4 days post inoculation with V275 at all but the lowest dose. The fourth instar larvae appeared to be less susceptible than earlier instars. There was good horizontal transmission of conidia from treated to un-inoculated larvae. However, mortality was higher in third and fourth instars and where the ratio of inoculated versus untreated larvae was high. This we presume is due to spores being more readily trapped by the urticating hairs found on third and older instar larvae. Injection of the nests offers a simple and environmentally friendly way of controlling the pest with reduced risk to operators.     

Tea stalks – a novel agro-residue for the production of tannase under solid state fermentation by Aspergillus niger JMU-TS528

A novel agro-residue, tea stalks, was tested for the production of tannase under solid-state fermentation (SSF) using Aspergillus niger JMU-TS528. Maximum yield of tannase was obtained when SSF was carried out at 28 °C, pH 6.0, liquid-to-solid ratio (v/w) 1.8, inoculum size 2 ml (1?×?10⁸ spores/ml), 5 % (w/v) ammonium chloride as nitrogen source and 5 % (w/v) lactose as additional carbon source. Under optimum conditions, tannase production reached 62 U/g dry substrate after 96 h of fermentation. Results from the study are promising for the economic utilization and value addition of tea stalks.     

Quantitative and qualitative aspects in the production of a nuclear polyhedrosis virus in Spodoptera exigua larvae

Spodoptera exigua nuclear polyhedrosis virus was produced in late fourth instar S. exigua larvae, reared on semi-artificial diet. A maximum amount of virus, 1–2 × 10⁹ polyhedra/larva, was produced in individually-reared larvae after 7 days of incubation, with an inoculum of 7–5 × 10⁴ polyhedra/cm² diet surface. Virus yield was slightly reduced to 9 × 10⁸ polyhedra/larva when production was carried out in groups of 400 and 600 larvae per container. Biological activity of virus harvested from living larvae and from dead cadavers was similar. Microbial contaminants, predominantly bacteria, in the virus product numbered 1–6% of the number of polyhedra. Tests for the presence of vertebrate-pathogenic bacteria in the virus product were all negative.     

Process optimization of xylanase production using cheap solid substrate by Trichoderma reesei SAF3 and study on the alteration of behavioral properties of enzyme obtained from SSF and SmF

This study aimed to assess the variability in respect of titer and properties of xylanase from Trichoderma reesei SAF3 under both solid-state and submerged fermentation. SSF was initially optimized with different agro-residues and among them wheat bran was found to be the best substrate that favored maximum xylanase production of 219 U (gws)^?1 at 96 h of incubation. The mycelial stage of the fungi and intracellular accumulation of Ca⁺⁺ and Mg⁺⁺ induced maximum enzyme synthesis. Inoculum level of 10 × 10⁶ spores 5 g^?1 of dry solid substrate and water activity of 0.6 were found to be optimum for xylanase production under SSF. Further optimization was made using a Box-Behnken design under response surface methodology. The optimal cultivation conditions predicted from canonical analysis of this model were incubation time (A) = 96–99 h, inoculum concentration (B) = 10 × 10⁶ spores 5 g^?1 of dry substrate, solid substrate concentration (C) = 10–12 g flask^?1, initial moisture level (D) = 10 mL flask^?1 (equivalent to a _w  = 0.55) and the level of xylanase was 299.7 U (gws)^?1. Subsequent verification of these levels agreed (97 % similar) with model predictions. Maximum amount of xylanase was recovered with water (6:1, v/w) and under shaking condition (125 rpm). Purified xylanase from SSF showed better stability in salt and pH, was catalytically and thermodynamically more efficient over enzyme from SmF, though molecular weight of both enzymes was identical (53.8 kDa).     

Experimental Vibriosis Induction with Vibrio alginolyticus of Larvae of the Catarina Scallop (Argopecten ventricosus =circularis) (Sowerby II, 1842)

Abstract Six-day-old larvae of the catarina scallop, Argopecten ventricosus (=circularis), were infected with different concentrations of Vibrio alginolyticus to determine virulence and to describe vibriosis in this species. The development of vibriosis was compared to the effect of the supernatant of a 24-h V. alginolyticus culture. An experimental larvae culture system (ELCS) yielded a maximum survival of 80% from the 6th to the 19th day (control and low concentrations of V. alginolyticus). No effect was shown with concentrations of V. alginolyticus below 0.5 × 10⁵ CFU ml⁻¹. At concentrations higher than 5.0 × 10⁵ CFU ml⁻¹, swimming depletion, empty stomachs, lipidic granules in the digestive system, velum degradation, and massive mortality were observed. The supernatant of V. alginolyticus culture showed similar effects to the highest concentrations of V. alginolyticus cells. Received: 13 November 1996; Accepted 28 March 1997     

Potential of a granulovirus isolate to control <Emphasis Type="Italic">Phthorimaea operculella</Emphasis> (Lepidoptera: Gelechiidae)

In this study a Brazilian granulovirus strain, PhopGV, isolated from the potato tuber moth (PTM) Phthorimaea operculella, was investigated regarding its potential for biological control and in vivo production. The relationship between mortality of P. operculella larvae and virus concentration was determined at different temperatures on potato tubers and susceptibility of P. operculella to PhopGV was also determined on potato leaves. Virulence of PhopGV to P. operculella was not affected by temperatures from 18 to 30°C. The median lethal concentration (LC₅₀) of larvae fed on potato foliage treated with PhopGV was not higher than that verified with larvae fed on treated tubers. Optimal conditions for production of virus-infected larvae were obtained by using the virus suspensions of 41 × 10⁵, 6.3 × 10⁵ and 62 × 10⁵ OBs ml⁻¹ at 18, 24 and 30°C, which resulted in 32.0, 31.4 and 34.8% of infected larvae collected, respectively. The maximum percentage of infected larvae recovered from tubers was not affected by temperature. However, time for production of virus-infected larvae was longer at 18°C and shorter at 30°C. Persistence of PhopGV was determined on stored tubers and we observed that the virus remained effective for at least two months, causing up to 84.2% mortality of P. operculella at 1 × 10⁷ OBs ml⁻¹. The pathogen was also highly virulent to tomato pinworm, Tuta absoluta, inflicting high percentage of mortality, delaying larval growth and inhibiting pupation. This Brazilian PhopGV strain has potential to control PTM larvae on potato tubers at a broad range of temperature and can be produced in vivo using virus-treated tubers.     

Comparison of SHF and SSF processes for the bioconversion of steam-exploded wheat straw

Two processes for ethanol production from wheat straw have been evaluated — separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). The study compares the ethanol yield for biomass subjected to varying steam explosion pretreatment conditions: temperature and time of pretreatment was 200°C or 217°C and at 3 or 10 min. A rinsing procedure with water and NaOH solutions was employed for removing lignin residues and the products of hemicellulose degradation from the biomass, resulting in a final structure that facilitated enzymatic hydrolysis. Biomass loading in the bioreactor ranged from 25 to 100 g l⁻¹ (dry weight). The enzyme-to-biomass mass ratio was 0.06. Ethanol yields close to 81% of theoretical were achieved in the two-step process (SHF) at hydrolysis and fermentation temperatures of 45°C and 37°C, respectively. The broth required addition of nutrients. Sterilisation of the biomass hydrolysate in SHF and of reaction medium in SSF can be avoided as can the use of different buffers in the two stages. The optimum temperature for the single-step process (SSF) was found to be 37°C and ethanol yields close to 68% of theoretical were achieved. The SSF process required a much shorter overall process time (≈30 h) than the SHF process (96 h) and resulted in a large increase in ethanol productivity (0.837 g l⁻¹ h⁻¹ for SSF compared to 0.313 g l⁻¹ h⁻¹ for SHF). Journal of Industrial Microbiology & Biotechnology (2000) 25, 184–192. Received 02 December 1999/ Accepted in revised form 20 July 2000