Rhizopus arrhizus - a producer for simultaneous saccharification and fermentation of starch waste materials to L(+)-lactic acid

Rhizopus arrhizus, strain DAR 36017, produced L(+)-lactic acid in a simultaneous saccharification and fermentation process using starch waste effluents. Lactic acid at 19.5 - 44.3 g l(-1) with a yield of 0.85 - 0.96 g g(-1) was produced in 40 h using 20 - 60 g starch l(-1). Supplementation of nitrogen source may be unnecessary if potato or corn starch waste effluent was used as a production medium.

Direct fermentation of potato starch in wastewater to lactic acid by Rhizopus oryzae

The fungal species of Rhizopus oryzae 2062 has the capacity to carry out a single stage fermentation process for lactic acid production from potato starch wastewater. Starch hydrolysis, reducing sugar accumulation, biomass formation, and lactic acid production were affected with variations in pH, temperature, and starch source and concentration. A growth condition with starch concentration approximately 20 g/L at pH 6.0 and 30degreesC was favourable for starch fermentation, resulting in a lactic acid yield of 78.3%similar to85.5% associated with 1.5similar to2.0 g/L fungal biomass produced in 36 h of fermentation.

Direct fermentation of potato starch wastewater to lactic acid by Rhizopus oryzae and Rhizopus arrhizus

The biochemical kinetic of direct fermentation for lactic acid production by fungal species of Rhizopus arrhizus 3,6017 and Rhizopus oryzae 2,062 was studied with respect to growth pH, temperature and substrate. The direct fermentation was characterized by starch hydrolysis, accumulation of reducing sugar, and production of lactic acid and fungal biomass. Starch hydrolysis, reducing sugar accumulation, biomass formation and lactic acid production were affected with the variations in pH, temperature, and starch source and concentration. A growth condition with starch concentration approximately 20 g/l at pH 6.0 and 30 degrees C was favourable for both starch saccharification and lactic acid fermentation, resulting in lactic acid yield of 0.87-0.97 g/g starch associated with 1.5-2.0 g/l fungal biomass produced in 36 h fermentation. R. arrhizus 3,6017 had a higher capacity to produce lactic acid, while R. oryzae 2,062 produced more fungal biomass under similar conditions.

A simulation model of cereal-legume intercropping systems for semi-arid regions I. Model development

Cereal-legume intercropping plays an important role in subsistence food production in developing countries, especially in situations of limited water resources. Crop simulation can be used to assess risk for intercrop productivity over time and space. In this study, a simple model for intercropping was developed for cereal and legume growth and yield, under semi-arid conditions. The model is based on radiation interception and use, and incorporates a water stress factor. Total dry matter and yield are functions of photosynthetically active radiation (PAR), the fraction of radiation intercepted and radiation use efficiency (RUE). One of two PAR sub-models was used to estimate PAR from solar radiation; either PAR is 50% of solar radiation or the ratio of PAR to solar radiation (PAR/SR) is a function of the clearness index (K-T). The fraction of radiation intercepted was calculated either based on Beer's Law with crop extinction coefficients (K) from field experiments or from previous reports. RUE was calculated as a function of available soil water to a depth of 900 mm (ASW). Either the soil water balance method or the decay curve approach was used to determine ASW. Thus, two alternatives for each of three factors, i.e., PAR/SR, K and ASW, were considered, giving eight possible models (2 methods x 3 factors). The model calibration and validation were carried out with maize-bean intercropping systems using data collected in a semi-arid region (Bloemfontein, Free State, South Africa) during seven growing seasons (1996/1997-2002/2003). The combination of PAR estimated from the clearness index, a crop extinction coefficient from the field experiment and the decay curve model gave the most reasonable and acceptable result. The intercrop model developed in this study is simple, so this modelling approach can be employed to develop other cereal-legume intercrop models for semi-arid regions. (c) 2004 Elsevier B.V. All rights reserved.

A simulation model of cereal-legume intercropping systems for semi-arid regions II. Model application

Smallholder farmers in Africa practice traditional cropping techniques such as intercropping. Intercropping is thought to offer higher productivity and resource milisation than sole cropping. In this study, risk associated with maize-bean intercropping was evaluated by quantifying long-term yield in both intercropping and sole cropping in a semi-arid region of South Africa (Bloemfontein, Free State) with reference to rainfall variability. The crop simulation model was run with different cultural practices (planting date and plant density) for 52 summer crop growing seasons (1950/1951-2001/2002). Eighty-one scenarios, consisted of three levels of initial soil water, planting date, maize population, and bean population, were simulated. From the simulation outputs, the total land equivalent ratio (LER) was greater than one. The intercrop (equivalent to sole maize) had greater energy value (EV) than sole beans, and the intercrop (equivalent to sole beans) had greater monetary value (MV) than sole maize. From these results, it can be concluded that maize-bean intercropping is advantageous for this semi-arid region. Soil water at planting was the most important factor of all scenario factors, followed by planting date. Irrigation application at planting, November/December planting and high plant density of maize for EV and beans for MV can be one of the most effective cultural practices in the study region. With regard to rainfall variability, seasonal (October-April) rainfall positively affected EV and MV, but not LER. There was more intercrop production in La Nina years than in El Nino years. Thus, better cultural practices may be selected to maximize maize-bean intercrop yields for specific seasons in the semi-arid region based on the global seasonal outlook. (c) 2004 Elsevier B.V. All rights reserved.

Piggery pond sludge as a nitrogen source for crops - 2. Assay of wet and stockpiled piggery pond sludge by successive cereal crops or direct measurement of soil available N

The appropriate use of wastes is a significant issue for the pig industry due to increasing pressure from regulatory authorities to protect the environment from pollution. Nitrogen contained in piggery pond sludge ( PPS) is a potential source of supplementary nutrient for crop production. Nitrogen contribution following the application of PPS to soil was obtained from 2 field experiments on the Darling Downs in southern Queensland on contrasting soil types, a cracking clay ( Vertosol) and a hardsetting sandy loam (Sodosol), and related to potentially mineralisable N from laboratory incubations conducted under controlled conditions and NO3- accumulation in the field. Piggery pond sludge was applied as-collected ( wet PPS) and following stockpiling to dry ( stockpiled PPS). Soil NO3- levels increased with increased application rates of wet and stockpiled PPS. Supplementary N supply from PPS estimated by fertiliser equivalence was generally unsatisfactory due to poor precision with this method, and also due to a high level of NO3- in the clay soil before the first assay crop. Also low recoveries of N by subsequent sorghum ( Sorghum bicolor) and wheat ( Triticum aestivum) assay crops at the 2 sites due to low in-crop rainfall in 1999 resulted in low apparent N availability. Over all, 29% ( range 12 - 47%) of total N from the wet PPS and 19% ( range 0 - 50%) from the stockpiled PPS were estimated to be plant-available N during the assay period. The high concentration of NO3- for the wet PPS application on sandy soil after the first assay crop ( 1998 barley, Hordeum vulgare) suggests that leaching of NO3- could be of concern when high rates of wet PPS are applied before infrequent periods of high precipitation, due primarily to the mineral N contained in wet PPS. Low yields, grain protein concentrations, and crop N uptake of the sorghum crop following the barley crop grown on the clay soil demonstrated a low residual value of N applied in PPS. NO3- in the sandy soil before sowing accounted for 79% of the variation in plant N uptake and was a better index than anaerobically mineralisable N ( 19% of variation explained). In clay soil, better prediction of crop N uptake was obtained when both anaerobically mineralisable N (39% of variation explained) and soil pro. le NO3- were used in combination (R-2 = 0.49).

Monensin supplementation of lactating cows fed tropical grasses and cane molasses or grain

Effects of monensin (Mon) on performance of Holstein-Friesian cows fed tropical grasses and cane molasses (M) or cereal grain were examined in three experiments. In experiment I (incomplete 4 x 4 Latin square), three rumen-fistulated cows [188 I I days in milk (DIM)] were fed mixed diets based on rhodes grass (Chloris gayana cv. Callide) bay where M was substituted for wheat grain (W) at rates of 0 (MO), 125 (M 125) or 250 (M250) g/kg dry matter (DM). A fourth diet contained M250 plus 0.02 g Mon/kg DM (M250 + Mon). Substituting M for W tended (P < 0.10) to decrease the ratio of rumen molar proportions of acetate+butyrate (Bu):propionate (Pr) (4.3 versus 3.8 and 4.0 for M0, M125 and M250, respectively). There were no treatment effects (P> 0.10) on intake, organic matter digestibility, milk production or liveweight (LW) change. In experiment 2, 48 cows (173 &PLUSMN; 28.3 DIM) grazing kikuyu (Pennisetum clandestinum cv. common) pastures and supplemented with maize silage and a grain-based concentrate were offered either M (2.6 kg DM/(cow day)) or barley grain (B) (2.7 kg DM/(cow day)). Within each supplement type, half were fed 0 or 320 mg of Mon/(cow day). There were Mon x supplement interactions (Mon x S; P < 0.05) on the rumen molar proportion of Pr and Bu at 15:00 h, with B + Mon having the highest value for Pr (0.259 mmol/mmol) and lowest value for Bu (0.121 mmol/mmol). A Mon x S effect (P < 0.05) on milk fat content was noted with Mon causing a lower value regardless of energy source (31 and 36 g/l versus 40 and 38 g/l for B + Mon, M + Mon, B - Mon and M - Mon, respectively). As a main effect, M as opposed to B, reduced yields of milk (P < 0.05; 16.21/(cow day) versus 18.01/(cow day)) and protein (P < 0.05; 479 g/(cow day) versus 538 g/(cow day)). Monensin reduced milk fat yield (P < 0.05; 669 g/(cow day) versus 562 g/(cow day)), raised milk protein concentration (P < 0.05; 31 g/l versus 29 g/l) and caused LW gain rather than loss (P < 0.05; +0.06 kg/(cow day) versus -0.30 kg/(cow day)). No treatment effects on pasture intake were noted. In experiment 3, 48 cows (91 &PLUSMN; 16.1 DIM) grazing kikuyu pasture and supplemented with grain-based concentrate, sugar cane silage and 2.7 kg DM(cow day) of M were supplemented with either 0 or 320 mg Mon/(cow day). Monensin reduced (P < 0.05) milk fat content (33 g/l versus 30 g/l) and tended (P < 0.10) to reduce milk protein content (29 g/l versus 28 g/l). No effects of Mon on other milk production parameters, LW change or pasture intake were noted. Feeding monensin to mid-lactation Holstein-Friesian cows offered diets based on tropical grasses, and cane molasses or grain, improves rumen fermentation efficiency, thereby improving energy efficiency resulting in higher LW gain. Monensin had no effect on milk yield, but reduced milk fat concentration.

Simultaneous saccharification and fermentation of potato starch wastewater to lactic acid by Rhizopus oryzae and Rhizopus arrhizus

The biochemical kinetic of simultaneous saccharification and fermentation (SSF) for lactic acid production by fungal species of Rhizopus arrhizus 36017 and Rhizopus oryzae 2062 was studied with respect to growth pH, temperature and substrate. Both R. arrhizus 36017 and R. oryzae 2062 had a capacity to carry out a single stage SSF process for lactic acid production from potato starch wastewater. The kinetic characteristics, termed as starch hydrolysis, accumulation of reducing sugars, lactic acid production and fungal biomass formation, were affected with variations in pH, temperature, and starch source and concentration. A growth condition with starch concentration approximately 20 g/l at pH 6.0 and 30 degrees C was favourable for both starch saccharification and lactic acid fermentation, resulting in lactic acid yield of 0.85-0.92 g/g associated with 1.5-3.5 g/l fungal biomass produced in 36-48 h fermentation. R. arrhizus 36017 had a higher capacity to produce lactic acid, while R. oryzae 2062 produced more fungal biomass under similar conditions. (c) 2005 Elsevier B.V. All rights reserved.

Comparison of gelation profile of yoghurts during fermentation measured by RVA and ultrasonic spectroscopy

The gelation profile of yoghurts from conventionally treated (85 degrees C/30 min) and UHT treated (143 degrees C/6s) milks at 16, 18, and 20% total solids was analyzed during fermentation for 4 hrs using the invasive Rapid Visco Analyzer (RVA) and the non-invasive ultrasonic spectroscope. The viscosity measured by the RVA and the ultrasonic velocity measured by the ultrasonic spectroscope exhibited similar sigmoid trends with respect to fermentation time. The ultrasonic spectroscope detected the onset of gelation of yoghurt milk earlier (by an average of 52 min) than did the RVA, indicating a higher sensitivity of ultrasonic spectroscopy. The delay of gelation time of UHT-treated yoghurt milk as compared to conventionally treated yoghurt milk was detected by both techniques. A non-significant ( P > 0.05) effect of solids content in the yoghurt milks on their gelation time was also observed by both instruments.