STATISTICAL MEDIA OPTIMIZATION FOR THE BIOMASS PRODUCTION OF POSTHARVEST BIOCONTROL YEAST Rhodosporidium paludigenum

A cane molasses-based medium for the biomass production of biocontrol agent Rhodosporidium paludigenum was statistically optimized. Molasses concentration (after pretreatment), yeast extract, and initial pH were identified by the Plackett–Burman design to show significant influence on the biomass production. The three factors were further optimized by central composite design and response-surface methodology. The statistical analysis indicated the optimum values of the variables were 89.98 g/L for cane molasses, 2.35 g/L for yeast extract and an initial pH of 8.48. The biomass yield at the optimal culture achieved 15.89 g/L in flask fermentation, which was 2.1 times higher than that at the initial NYDB medium. In a 10-L fermenter, 18.97 g/L of biomass was obtained after 36 hr of cultivation. Moreover, the biocontrol efficacy of the yeast was investigated after culture optimization. The results showed the yeast harvested in the optimal medium maintained its initial biocontrol properties by reducing the percentage of decayed apples to below 20%.     

Nutritional composition of black soldier fly larvae feeding on agro-industrial by-products

Black soldier fly (BSF) larvae, Hermetia illucens L. (Diptera: Stratiomyidae), bio-convert organic side streams into high-quality biomass, the composition of which largely depends on the side stream used. In the present study, BSF larvae were reared on feed substrates composed of dried brewers’ spent grains, each supplemented with either water, waste brewer’s yeast, or a mixture of waste brewer’s yeast and cane molasses to obtain 12 different substrates: barley/water, barley/yeast, barley/yeast/molasses, malted barley/water, malted barley/yeast, malted barley/yeast/molasses, malted corn/water, malted corn/yeast, malted corn/yeast/molasses, sorghum-barley/water, sorghum-barley/yeast, and sorghum-barley/yeast/molasses. The crude protein, fat, ash, and mineral contents of the BSF larvae fed each feed substrate were quantified by chemical analyses. The effect of substrate, supplementation, and their interaction on crude protein, fat, and ash contents of BSF larval body composition was significant. Calcium, phosphorus, and potassium were the most abundant macrominerals in the larvae and their concentrations differed significantly among substrates. These findings provide important information to support the use of BSF larval meal as potential new source of nutrient-rich and sustainable animal feed ingredients to substitute expensive and scarce protein sources such as fishmeal and soya bean meal.     

Development of food-grade expression system for d-allulose 3-epimerase preparation with tandem isoenzyme genes in Corynebacterium glutamicum and its application in conversion of cane molasses to D-allulose

D -Allulose 3-epimerase (DAE) has been applied to produce D -allulose, a low-calorie and functional sweetener. In this study, a new DAE from Paenibacillus senegalensis was characterized in Escherichia coli. Furthermore, we presented a tandem isoenzyme gene expression strategy to express multiple DAEs in one cell and construct food-grade expression systems based on Corynebacterium glutamicum. Seventeen expression cassettes based on three DAE genes from different organisms were constructed. Among all recombinant strains, DAE16 harboring three DAE genes in an expression vector exhibited the highest enzyme activity with 22.7 U/mg. Whole-cell transformation of DAE16 produced 225 g/L D -allulose with a volumetric productivity of 353 g·g ⁻¹·hr ⁻¹. The catalytic efficiency of strain C-DAE9 integrating total 11 DAE genes in chromosome was 16.4-fold higher than strains carrying one DAE. Fed-batch culture of C-DAE9 gave enzyme activity of 44,700 U/L. We also expressed a thermostable invertase in C. glutamicum and obtained enzyme activity of 29 U/mg. Immobilized cells expressing DAE or invertase exhibited 80% of retained activity after 30 cycles of catalytic reactions. Those immobilized cells were coupled to produce 61.2 g/L D -allulose from cane molasses in a two-step reaction process. This study provided an efficient approach for enzyme preparation and allowed access to produce D -allulose from other abundant and low-cost feedstock enriched with sucrose.     

beta-Carotene production in sugarcane molasses by a Rhodotorula glutinis mutant

Several wild strains and mutants of Rhodotorula spp. were screened for growth, carotenoid production and the proportion of -carotene produced in sugarcane molasses. A better producer, Rhodotorula glutinis mutant 32, was optimized for carotenoid production with respect to total reducing sugar (TRS) concentration and pH. In shake flasks, when molasses was used as the sole nutrient medium with 40 g l⁻¹ TRS, at pH 6, the carotenoid yield was 14 mg l⁻¹ and -carotene accounted for 70% of the total carotenoids. In a 14-l stirred tank fermenter, a 20% increase in torulene content was observed in plain molasses medium. However, by addition of yeast extract, this effect was reversed and a 31% increase in -carotene content was observed. Dissolved oxygen (DO) stat fed-batch cultivation of mutant 32 in plain molasses medium yielded 71 and 185 mg l⁻¹ total carotenoids in double- and triple-strength medium, respectively. When supplemented with yeast extract, the yields were 97 and 183 mg l⁻¹ total carotenoid with a 30% increase in -carotene and a simultaneous 40% decrease in torulene proportion. Higher cell mass was also achieved by double- and triple-strength fed-batch fermentation. Journal of Industrial Microbiology & Biotechnology (2001) 26, 327–332. Received 18 September 2000/ Accepted in revised form 02 March 2001     

The use of tamarind waste to improve ethanol production from cane molasses

Tamarind wastes such as tamarind husk, pulp, seeds, fruit and the effluent generated during tartaric acid extraction were used as supplements to evaluate their effects on alcohol production from cane molasses using yeast cultures. Small amounts of these additives enhanced the rate of ethanol production in batch fermentations. Tamarind fruit increased ethanol production (9.7%, w/v) from 22.5% reducing sugars of molasses as compared to 6.5% (w/v) in control experiments lacking supplements after 72 h of fermentation. In general, the addition of tamarind supplements to the fermentation medium showed more than 40% improvement in ethanol production using higher cane molasses sugar concentrations. The direct fermentation of aqueous tamarind effluent also yielded 3.25% (w/v) ethanol, suggesting its possible use as a diluent in molasses fermentations. This is the first report, to our knowledge, in which tamarind-based waste products were used in ethanol production. Received 2 April 1998/ Accepted in revised form 13 November 1998     

利用甜菜糖蜜补料发酵生产丁醇

从土壤中分离出1株适合利用甜菜糖蜜发酵生产丁醇的丙酮丁醇梭菌(Clostridium acetobutylicum)2N,通过优化发酵条件,得到最适发酵温度为33℃,玉米浆最适添加量为15g/L,发现甜菜糖蜜中还原糖质量浓度高于50g/L时影响菌株的生长和溶剂生产。以补料分批发酵方式降低底物抑制,33℃发酵48h后,丁醇和总溶剂的质量浓度分别达到14.15g/L和19.65g/L,丁醇质量分数超过70%。     

Production of <Emphasis Type="SmallCaps">d</Emphasis>-lactic acid from sugarcane molasses,sugarcane juice and sugar beet juice by <Emphasis Type="Italic">Lactobacillus delbrueckii</Emphasis>

Lactobacillus delbrueckii was grown on sugarcane molasses, sugarcane juice and sugar beet juice in batch fermentation at pH 6 and at 40°C. After 72 h, the lactic acid from 13% (w/v) sugarcane molasses (119 g total sugar l⁻¹) and sugarcane juice (133 g total sugar l⁻¹) was 107 g l⁻¹ and 120 g l⁻¹, respectively. With 10% (w/v) sugar beet juice (105 g total sugar l⁻¹), 84 g lactic acid l⁻¹ was produced. The optical purities of d-lactic acid from the feedstocks ranged from 97.2 to 98.3%.     

产氢新菌Ethanoligenens sp. B49发酵糖蜜制氢条件

研究1株产氢细菌Ethanoligenens sp.B49利用废糖蜜为基本原料进行生物制氢的条件,及外加氮素营养物对废糖蜜生物制氢的影响.结果表明,在10.3～20.6 g·L-1的化学需氧量(COD)范围内,经过驯化的Ethanoligenens sp.B49细胞具有较好的生物利用能力,细胞生长量和产氢能力随着废糖蜜COD的提高而增加.当废糖蜜COD超过20.6 g·L-1时Ethanoligenens sp.B49的细胞生长受到抑制,同时产氢能力下降,COD超过41.2 g·L-1时细胞基本不具有生长和产氢能力.Ethanoligenens sp.B49利用废糖蜜产氢的最佳COD为20.6 g·L-1.在20.6 g·L-1COD条件下外加有机氮源可以促进Ethanoligenens sp.B49利用废糖蜜制氢的能力,促进作用顺序为酵母粉＞牛肉膏＞蛋白胨＞脲素.添加4 g·L-1的酵母粉时,Ethanoligenens sp.B49细胞具有最好的生长活性和产氢能力.优化营养条件后,单位体积产氢量从44.82 mmol·L-1提高到78.97 mmol·L-1,提高了76.2%.