Repeated batch fermentation with water recycling and cell separation for microbial lipid production

Large waste water disposal was the major problem in microbial lipid fermentation because of low yield of lipid. In this study, the repeated batch fermentation was investigated for reducing waste water generated in the lipid fermentation of an oleaginous yeast Trichosporon cutaneum CX1 strain. The waste fermentation broth was recycled in the next batch operation after the cells were separated using two different methods, centrifugation and flocculation. Two different sugar substrates, glucose and inulin, were applied to the proposed operation. The result showed that at least 70% of the waste water was reduced, while lipid production maintained satisfactory in the initial four cycles. Furthermore, it is suggested that T. cutaneum CX1 cells might produce certain naturally occurring inulin hydrolyzing enzyme（s） for obtaining fructose and glucose from inulin directly. Our method provided a practical option for reducing the waste water generated from microbial lipid fermentation.

Biodiesel production from microbial lipid obtained by intermittent feeding of municipal sludge and treated crude glycerol

In the present study,municipal secondary sludge and purified glycerol(obtained after acid treatment of crude glycerol)were used together for lipid production using intermittent feeding strategy.Intermittent sludge feeding strategy(sludge SS 30 g/L)resulted in a higher biomass(54.99 g/L)and lipid concentration(25.35 g/L)at 96 h when compared to 35 g/L SS single sludge feeding or control strategy(45.67 g/L biomass&19.16 g/L lipid).Moreover,the intermittent sludge feeding strategy significantly reduced foaming and requirement of anti-foam during fermentation when compared to control strategy.The energy balance of biodiesel production from lipid obtained by intermittent sludge feeding strategy(30 g/L SS)was energeti-cally favorable.It was also revealed from yield coefficients and energy balance that sludge had an important contribution in microbial lipid and biodiesel production.

Optimization of trace elements in purified glycerol for microbial lipid and citric acid production by Yarrowia lipolytica SKY7

Purified glycerol obtained after acid treatment of crude glycerol solution was used as the carbon source for lipid and citric acid production using Y.lipolytica SKY7.Although purified glycerol was high in phosphorus,it was important to inves-tigate the impact of fortification of trace elements in the medium on cell growth,lipid and citric acid(CA)production.When all the trace elements(including phosphates and sulfates)required for growth and lipid production were added to the purified glycerol medium,high biomass(51.67 g/L)and lipid concentration(19.47 g/L)were observed at 96 h of fed-batch fermentation with low CA concentration of 5.42 g/L.The purified glycerol medium without additional trace elements gave low biomass(27.67 g/L),lipid concentration(9.35 g/L)at 80 h of fed-batch fermentation,but gave high CA concentration(24.51 g/L).When purified glycerol was provided with only sulfates or all elements except KH_(2)PO_(4),low biomass(32.59 g/L and 38.52 g/L)and citric acid concentration(1 g/L and 2.42 g/L)were obtained at 96 h.

Improving lipid production by Rhodotorula glutinis for renewable fuel production based on machine learning

Microbial lipid fermentation encompasses intricate complex cell growth processes and heavily relies on expert experience for optimal production.Digital modeling of the fermentation process assists researchers in making intelligent decisions,employing logical reasoning and strategic planning to optimize lipid fermentation.It this study,the effects of medium components and concen-trations on lipid fermentation were investigated,first.And then,leveraging the collated data,a variety of machine learning algorithms were used to model and optimize the lipid fermentation process.The models,based on artificial neural networks and support vector machines,achieved R?values all higher than 0.93,ensuring accurate predictions of the fermentation process.Multiple linear regression was used to evaluate the respective target parameter,which were affected by the medium components of lipid fermentation.Lastly,single and multi-objective optimiza-tion were conducted for lipid fermentation using the genetic algorithm.Experimental results demonstrated the maximum biomass of 50.3 g·L^(-1) and maximum lipid concentration of 14.1 g:L^(-1) with the error between the experimental and predicted values less than 5%.The results of the multi-objective optimization reveal the synergistic and competitive relationship between biomass,lipid concentration,and conversion rate,which lay a basis for in-depth optimization and amplification.

Utilization of Soluble Starch by Oleaginous Red Yeast Rhodotorula glutinis

Starch containing wastewaters from the food and feed industry have been identified as potential cheap carbon sources for the production of microbial lipids. Due to its high potential lipid content the oleaginous yeast Rhodotorula glutinis is often used for fermentations in this field. Moreover it is investigated in the context of microbial carotenoid production, which also requires a cheap source of carbon. Thus, the ability of R. glutinis (ATCC 15125TM) to degrade and utilize soluble starch for the production of lipids has been assessed in this study. While glucose and fructose were readily consumed from the medium, starch was only slightly reduced in one treatment. The yield of fatty acid methyl esters (FAME) was graduated corresponding to the initial sugar contents, with the highest FAME yield (1.5 g·L-1) at the highest initial sugar content. In the treatment that contained starch as single carbon source, no FAME production was realized. Accordingly, if starchy wastewaters should be used for microbial cultivation with R. glutinis, an enzymatic or chemical pretreatment for starch hydrolysis should be applied, to increase the availability of this carbon source.

Biotechnological valorization of biodiesel-derived glycerol: Trials with the non-conventional yeasts Yarrowia lipolytica and Rhodosporidium sp

Four non-conventional yeast strains belonging to the genera Yarrowia and Rhodosporidium were cultivated under nitrogen-limited conditions in shake flasks with biodiesel-derived glycerol employed as sole substrate.The strains R.toruloides DSM 4444 and Y.lipolytica ACA-DC 5033 displayed better performances and were further studied.At initial glycerol(Gly0)≈50 g/L,the strain ACA-DC 5033 produced dry cell weight(DCW)≈7.0 g/L,and also secondary extra-cellular metabolites as citric acid(CA)at≈16 g/L and polyols(Pol)(mannitol,erythritol and arabitol)at≈21 g/L.In double-media(besides nitrogen also Mg was limiting)for Gly0≈50 g/L,a shift towards CA production occurred(CAmax≈33 g/L).The strain DSM 4444 at Gly0≈50 g/L produced DCW=18.1 g/L containing lipids=30.3%in DCW.In single nitrogen-limited media with Gly0≈90 g/L,the strain ACA-DC 5033 produced Pol≈48 g/L and CA≈20 g/L,while the strain DSM 4444 produced DCW=27.3 g/L containing lipid=54.5%w/w.At the late growth phases,metabolites were re-consumed.Balanced growth phase(trophophase)and phase of secondary metabolite synthesis(idiophase)were successfully simulated with the aid of a modified Velhlust-Aggelis model.Lipid extraction process was studied for these two strains by using two different extraction methods.Yeast lipids contained mostly oleic acid,constituting suitable precursors for the synthesis of 2nd generation biodiesel.